Various attacks cause ability score loss, either ability damage or ability drain. Points lost to ability damage return at the rate of 1 point per day (or double that if the character gets complete bed rest) to each damaged ability, and the spells lesser restoration and restoration offset ability damage as well. Ability drain, however, is permanent, though restoration can restore even those lost ability score points.

While any loss is debilitating, losing all points in an ability score can be devastating.

Keeping track of negative ability score points is never necessary. A character's ability score can't drop below 0.

Having a score of 0 in an ability is different from having no ability score whatsoever.

Some spells or abilities impose an effective ability score reduction, which is different from ability score loss. Any such reduction disappears at the end of the spell's or ability's duration, and the ability score immediately returns to its former value.

If a character's Constitution score drops, then he loses 1 hit point per Hit Die for every point by which his Constitution modifier drops. A hit point score can't be reduced by Constitution damage or drain to less than 1 hit point per Hit Die.

The ability that some creatures have to drain ability scores is a supernatural one, requiring some sort of attack. Such creatures do not drain abilities from enemies when the enemies strike them, even with unarmed attacks or natural weapons.

An antimagic field spell or effect cancels magic altogether. An antimagic effect has the following powers and characteristics.

Some creatures have blindsight, the extraordinary ability to use a nonvisual sense (or a combination of such senses) to operate effectively without vision. Such sense may include sensitivity to vibrations, acute scent, keen hearing, or echolocation. This ability makes invisibility and concealment (even magical darkness) irrelevant to the creature (though it still can't see ethereal creatures). This ability operates out to a range specified in the creature description.

A creature attacking with a breath weapon is actually expelling something from its mouth (rather than conjuring it by means of a spell or some other magical effect). Most creatures with breath weapons are limited to a number of uses per day or by a minimum length of time that must pass between uses. Such creatures are usually smart enough to save their breath weapon until they really need it.

Many abilities and spells can cloud the minds of characters and monsters, leaving them unable to tell friend from foe-or worse yet, deceiving them into thinking that their former friends are now their worst enemies. Two general types of enchantments affect characters and creatures: charms and compulsions.

Charming another creature gives the charming character the ability to befriend and suggest courses of actions to his minion, but the servitude is not absolute or mindless. Charms of this type include the various charm spells. Essentially, a charmed character retains free will but makes choices according to a skewed view of the world.

Compulsion is a different matter altogether. A compulsion overrides the subject's free will in some way or simply changes the way the subject's mind works. A charm makes the subject a friend of the caster; a compulsion makes the subject obey the caster.

Regardless of whether a character is charmed or compelled, he won't volunteer information or tactics that his master doesn't ask for.

A creature with cold immunity never takes cold damage. It has vulnerability to fire, which means it takes half again as much (+50%) damage as normal from fire, regardless of whether a saving throw is allowed, or if the save is a success or failure.

Some magic creatures have the supernatural ability to instantly heal damage from weapons or to ignore blows altogether as though they were invulnerable.

The numerical part of a creature's damage reduction is the amount of hit points the creature ignores from normal attacks. Usually, a certain type of weapon can overcome this reduction. This information is separated from the damage reduction number by a slash. Damage reduction may be overcome by special materials, by magic weapons (any weapon with a +1 or higher enhancement bonus, not counting the enhancement from masterwork quality), certain types of weapons (such as slashing or bludgeoning), and weapons imbued with an alignment. If a dash follows the slash then the damage reduction is effective against any attack that does not ignore damage reduction.

Ammunition fired from a projectile weapon with an enhancement bonus of +1 or higher is treated as a magic weapon for the purpose of overcoming damage reduction. Similarly, ammunition fired from a projectile weapon with an alignment gains the alignment of that projectile weapon (in addition to any alignment it may already have).

Whenever damage reduction completely negates the damage from an attack, it also negates most special effects that accompany the attack, such as injury type poison, a monk's stunning, and injury type disease. Damage reduction does not negate touch attacks, energy damage dealt along with an attack, or energy drains. Nor does it affect poisons or diseases delivered by inhalation, ingestion, or contact.

Attacks that deal no damage because of the target's damage reduction do not disrupt spells.

Spells, spell-like abilities, and energy attacks (even nonmagical fire) ignore damage reduction.

Sometimes damage reduction is instant healing. Sometimes damage reduction represents the creature's tough hide or body,. In either case, characters can see that conventional attacks don't work.

If a creature has damage reduction from more than one source, the two forms of damage reduction do not stack. Instead, the creature gets the benefit of the best damage reduction in a given situation.

Darkvision is the extraordinary ability to see with no light source at all, out to a range specified for the creature. Darkvision is black and white only (colors cannot be discerned). It does not allow characters to see anything that they could not see otherwise-invisible objects are still invisible, and illusions are still visible as what they seem to be. Likewise, darkvision subjects a creature to gaze attacks normally. The presence of light does not spoil darkvision.

In most cases, a death attack allows the victim a Fortitude save to avoid the affect, but if the save fails, the character dies instantly.

When a character is injured by a contaminated attack touches an item smeared with diseased matter, or consumes disease-tainted food or drink, he must make an immediate Fortitude saving throw. If he succeeds, the disease has no effect-his immune system fought off the infection. If he fails, he takes damage after an incubation period. Once per day afterward, he must make a successful Fortitude saving throw to avoid repeated damage. Two successful saving throws in a row indicate that he has fought off the disease and recovers, taking no more damage.

These Fortitude saving throws can be rolled secretly so that the player doesn't know whether the disease has taken hold.

Some horrible creatures, especially undead monsters, possess a fearsome supernatural ability to drain levels from those they strike in combat. The creature making an energy drain attack draws a portion of its victim's life force from her. Most energy drain attacks require a successful melee attack roll-mere physical contact is not enough. Each successful energy drain attack bestows one or more negative levels on the opponent. A creature takes the following penalties for each negative level it has gained.

-1 on all skill checks and ability checks.

-1 on attack rolls and saving throws.

-5 hit points.

-1 effective level (whenever the creature's level is used in a die roll or calculation, reduce it by one for each negative level).

If the victim casts spells, she loses access to one spell as if she had cast her highest-level, currently available spell. (If she has more than one spell at her highest level, she chooses which she loses.) In addition, when she next prepares spells or regains spell slots, she gets one less spell slot at her highest spell level.

Negative levels remain for 24 hours or until removed with a spell, such as restoration. After 24 hours, the afflicted creature must attempt a Fortitude save (DC 10 + 1/2 attacker's HD + attacker's Cha modifier). (The DC is provided in the attacker's description.) If the saving throw succeeds, the negative level goes away with no harm to the creature. The afflicted creature makes a separate saving throw for each negative level it has gained. If the save fails, the negative level goes away, but the creature's level is also reduced by one.

A character with negative levels at least equal to her current level, or drained below 1st level, is instantly slain. Depending on the creature that killed her, she may rise the next night as a monster of that kind. If not, she rises as a wight. A creature gains 5 temporary hit points for each negative level it bestows (though not if the negative level is caused by a spell or similar effect).

Phase spiders and certain other creatures can exist on the Ethereal Plane. While on the Ethereal Plane, a creature is called ethereal. Unlike incorporeal creatures, ethereal creatures are not present on the Material Plane.

Ethereal creatures are invisible, inaudible, insubstantial, and scentless to creatures on the Material Plane. Even most magical attacks have no effect on them. See invisibility and true seeing reveal ethereal creatures.

An ethereal creature can see and hear into the Material Plane in a 60-foot radius, though material objects still block sight and sound. (An ethereal creature can't see through a material wall, for instance.) An ethereal creature inside an object on the Material Plane cannot see. Things on the Material Plane, however, look gray, indistinct, and ghostly. An ethereal creature can't affect the Material Plane, not even magically. An ethereal creature, however, interacts with other ethereal creatures and objects the way material creatures interact with material creatures and objects.

Even if a creature on the Material Plane can see an ethereal creature the ethereal creature is on another plane. Only force effects can affect the ethereal creatures. If, on the other hand, both creatures are ethereal, they can affect each other normally.

A force effect originating on the Material Plane extends onto the Ethereal Plane, so that a wall of force blocks an ethereal creature, and a magic missile can strike one (provided the spellcaster can see the ethereal target). Gaze effects and abjurations also extend from the Material Plane to the Ethereal Plane. None of these effects extend from the Ethereal Plane to the Material Plane.

Ethereal creatures move in any direction (including up or down) at will. They do not need to walk on the ground, and material objects don't block them (though they can't see while their eyes are within solid material).

Ghosts have a power called manifestation that allows them to appear on the Material Plane as incorporeal creatures. Still, they are on the Ethereal Plane, and another ethereal creature can interact normally with a manifesting ghost. Ethereal creatures pass through and operate in water as easily as air. Ethereal creatures do not fall or take falling damage.

These extraordinary abilities allow the target of an area attack to leap or twist out of the way. Rogues and monks have evasion and improved evasion as class features, but certain other creatures have these abilities, too.

If subjected to an attack that allows a Reflex save for half damage, a character with evasion takes no damage on a successful save.

As with a Reflex save for any creature, a character must have room to move in order to evade. A bound character or one squeezing through an area cannot use evasion.

As with a Reflex save for any creature, evasion is a reflexive ability. The character need not know that the attack is coming to use evasion.

Rogues and monks cannot use evasion in medium or heavy armor. Some creatures with the evasion ability as an innate quality do not have this limitation.

Improved evasion is like evasion, except that even on a failed saving throw the character takes only half damage.

A creature with fast healing has the extraordinary ability to regain hit points at an exceptional rate. Except for what is noted here, fast healing is like natural healing.

At the beginning of each of the creature's turns, it heals a certain number of hit points (defined in its description).

Unlike regeneration, fast healing does not allow a creature to regrow or reattach lost body parts.

A creature that has taken both nonlethal and lethal damage heals the nonlethal damage first.

Fast healing does not restore hit points lost from starvation, thirst, or suffocation.

Fast healing does not increase the number of hit points regained when a creature polymorphs.

Spells, magic items, and certain monsters can affect characters with fear. In most cases, the character makes a Will saving throw to resist this effect, and a failed roll means that the character is shaken, frightened, or panicked.

A creature with fire immunity never takes fire damage. It has vulnerability to cold, which means it takes half again as much (+50%) damage as normal from cold, regardless of whether a saving throw is allowed, or if the save is a success or failure.

Some creatures have the supernatural or spell-like ability to take the form of a cloud of vapor or gas.

Creatures in gaseous form can't run but can fly. A gaseous creature can move about and do the things that a cloud of gas can conceivably do, such as flow through the crack under a door. It can't, however, pass through solid matter. Gaseous creatures can't attack physically or cast spells with verbal, somatic, material, or focus components. They lose their supernatural abilities (except for the supernatural ability to assume gaseous form, of course).

Creatures in gaseous form have damage reduction 10/magic. Spells, spell-like abilities, and supernatural abilities affect them normally. Creatures in gaseous form lose all benefit of material armor (including natural armor), though size, Dexterity, deflection bonuses, and armor bonuses from force armor still apply.

Gaseous creatures do not need to breathe and are immune to attacks involving breathing (troglodyte stench, poison gas, and the like).

Gaseous creatures can't enter water or other liquid. They are not ethereal or incorporeal. They are affected by winds or other forms of moving air to the extent that the wind pushes them in the direction the wind is moving. However, even the strongest wind can't disperse or damage a creature in gaseous form.

Discerning a creature in gaseous form from natural mist requires a DC 15 Spot check. Creatures in gaseous form attempting to hide in an area with mist, smoke, or other gas gain a +20 bonus.

While the medusa's gaze is well known, gaze attacks can also charm, curse, or even kill. Gaze attacks not produced by a spell are supernatural.

Each character within range of a gaze attack must attempt a saving throw (which can be a Fortitude or Will save) each round at the beginning of his turn.

An opponent can avert his eyes from the creature's face, looking at the creature's body, watching its shadow, or tracking the creature in a reflective surface. Each round, the opponent has a 50% chance of not having to make a saving throw. The creature with the gaze attack gains concealment relative to the opponent. An opponent can shut his eyes, turn his back on the creature, or wear a blindfold. In these cases, the opponent does not need to make a saving throw. The creature with the gaze attack gains total concealment relative to the opponent.

A creature with a gaze attack can actively attempt to use its gaze as an attack action. The creature simply chooses a target within range, and that opponent must attempt a saving throw. If the target has chosen to defend against the gaze as discussed above, the opponent gets a chance to avoid the saving throw (either 50% chance for averting eyes or 100% chance for shutting eyes). It is possible for an opponent to save against a creature's gaze twice during the same round, once before its own action and once during the creature's action.

Looking at the creature's image (such as in a mirror or as part of an illusion) does not subject the viewer to a gaze attack.

A creature is immune to its own gaze attack.

If visibility is limited (by dim lighting, a fog, or the like) so that it results in concealment, there is a percentage chance equal to the normal miss chance for that degree of concealment that a character won't need to make a saving throw in a given round. This chance is not cumulative with the chance for averting your eyes, but is rolled separately.

Invisible creatures cannot use gaze attacks.

Characters using darkvision in complete darkness are affected by a gaze attack normally.

Unless specified otherwise, a creature with a gaze attack can control its gaze attack and 'turn it off ' when so desired.

Spectres, wraiths, and a few other creatures lack physical bodies. Such creatures are insubstantial and can't be touched by nonmagical matter or energy. Likewise, they cannot manipulate objects or exert physical force on objects. However, incorporeal beings have a tangible presence that sometimes seems like a physical attack against a corporeal creature.

Incorporeal creatures are present on the same plane as the characters, and characters have some chance to affect them.

Incorporeal creatures can be harmed only by other incorporeal creatures, by magic weapons, or by spells, spell-like effects, or supernatural effects. They are immune to all nonmagical attack forms. They are not burned by normal fires, affected by natural cold, or harmed by mundane acids.

Even when struck by magic or magic weapons, an incorporeal creature has a 50% chance to ignore any damage from a corporeal source-except for a force effect or damage dealt by a ghost touch weapon.

Incorporeal creatures are immune to critical hits, extra damage from being favored enemies, and from sneak attacks. They move in any direction (including up or down) at will. They do not need to walk on the ground. They can pass through solid objects at will, although they cannot see when their eyes are within solid matter.

Incorporeal creatures hiding inside solid objects get a +2 circumstance bonus on Listen checks, because solid objects carry sound well. Pinpointing an opponent from inside a solid object uses the same rules as pinpointing invisible opponents (see Invisibility, below).

Incorporeal creatures are inaudible unless they decide to make noise.

The physical attacks of incorporeal creatures ignore material armor, even magic armor, unless it is made of force (such as mage armor or bracers of armor) or has the ghost touch ability.

Incorporeal creatures pass through and operate in water as easily as they do in air.

Incorporeal creatures cannot fall or take falling damage.

Corporeal creatures cannot trip or grapple incorporeal creatures.

Incorporeal creatures have no weight and do not set off traps that are triggered by weight.

Incorporeal creatures do not leave footprints, have no scent, and make no noise unless they manifest, and even then they only make noise intentionally.

The ability to move about unseen is not foolproof. While they can't be seen, invisible creatures can be heard, smelled, or felt.

Invisibility makes a creature undetectable by vision, including darkvision.

Invisibility does not, by itself, make a creature immune to critical hits, but it does make the creature immune to extra damage from being a ranger's favored enemy and from sneak attacks.

A creature can generally notice the presence of an active invisible creature within 30 feet with a DC 20 Spot check. The observer gains a hunch that 'something's there' but can't see it or target it accurately with an attack. A creature who is holding still is very hard to notice (DC 30). An inanimate object, an unliving creature holding still, or a completely immobile creature is even harder to spot (DC 40). It's practically impossible (+20 DC) to pinpoint an invisible creature's location with a Spot check, and even if a character succeeds on such a check, the invisible creature still benefits from total concealment (50% miss chance).

A creature can use hearing to find an invisible creature. A character can make a Listen check for this purpose as a free action each round. A Listen check result at least equal to the invisible creature's Move Silently check result reveals its presence. (A creature with no ranks in Move Silently makes a Move Silently check as a Dexterity check to which an armor check penalty applies.) A successful check lets a character hear an invisible creature 'over there somewhere.' It's practically impossible to pinpoint the location of an invisible creature. A Listen check that beats the DC by 20 pinpoints the invisible creature's location.

A creature can grope about to find an invisible creature. A character can make a touch attack with his hands or a weapon into two adjacent 5-foot squares using a standard action. If an invisible target is in the designated area, there is a 50% miss chance on the touch attack. If successful, the groping character deals no damage but has successfully pinpointed the invisible creature's current location. (If the invisible creature moves, its location, obviously, is once again unknown.)

If an invisible creature strikes a character, the character struck still knows the location of the creature that struck him (until, of course, the invisible creature moves). The only exception is if the invisible creature has a reach greater than 5 feet. In this case, the struck character knows the general location of the creature but has not pinpointed the exact location.

If a character tries to attack an invisible creature whose location he has pinpointed, he attacks normally, but the invisible creature still benefits from full concealment (and thus a 50% miss chance). A particularly large and slow creature might get a smaller miss chance.

If a character tries to attack an invisible creature whose location he has not pinpointed, have the player choose the space where the character will direct the attack. If the invisible creature is there, conduct the attack normally. If the enemy's not there, roll the miss chance as if it were there, don't let the player see the result, and tell him that the character has missed. That way the player doesn't know whether the attack missed because the enemy's not there or because you successfully rolled the miss chance.

If an invisible character picks up a visible object, the object remains visible. One could coat an invisible object with flour to at least keep track of its position (until the flour fell off or blew away). An invisible creature can pick up a small visible item and hide it on his person (tucked in a pocket or behind a cloak) and render it effectively invisible.

Invisible creatures leave tracks. They can be tracked normally. Footprints in sand, mud, or other soft surfaces can give enemies clues to an invisible creature's location.

An invisible creature in the water displaces water, revealing its location. The invisible creature, however, is still hard to see and benefits from concealment.

A creature with the scent ability can detect an invisible creature as it would a visible one.

A creature with the Blind-Fight feat has a better chance to hit an invisible creature. Roll the miss chance twice, and he misses only if both rolls indicate a miss. (Alternatively, make one 25% miss chance roll rather than two 50% miss chance rolls.)

A creature with blindsight can attack (and otherwise interact with) creatures regardless of invisibility.

An invisible burning torch still gives off light, as does an invisible object with a light spell (or similar spell) cast upon it.

Ethereal creatures are invisible. Since ethereal creatures are not materially present, Spot checks, Listen checks, Scent, Blind-Fight, and blindsight don't help locate them. Incorporeal creatures are often invisible. Scent, Blind-Fight, and blindsight don't help creatures find or attack invisible, incorporeal creatures, but Spot checks and possibly Listen checks can help.

Invisible creatures cannot use gaze attacks.

Invisibility does not thwart detect spells.

Since some creatures can detect or even see invisible creatures, it is helpful to be able to hide even when invisible.

A character who loses a level instantly loses one Hit Die. The character's base attack bonus, base saving throw bonuses, and special class abilities are now reduced to the new, lower level. Likewise, the character loses any ability score gain, skill ranks, and any feat associated with the level (if applicable). If the exact ability score or skill ranks increased from a level now lost is unknown (or the player has forgotten), lose 1 point from the highest ability score or ranks from the highest-ranked skills. If a familiar or companion creature has abilities tied to a character who has lost a level, the creature's abilities are adjusted to fit the character's new level.

The victim's experience point total is immediately set to the midpoint of the previous level.

Characters with low-light vision have eyes that are so sensitive to light that they can see twice as far as normal in dim light. Low-light vision is color vision. A spellcaster with low-light vision can read a scroll as long as even the tiniest candle flame is next to her as a source of light.

Characters with low-light vision can see outdoors on a moonlit night as well as they can during the day.

Some monsters and spells have the supernatural or spell-like ability to paralyze their victims, immobilizing them through magical means. (Paralysis from toxins is discussed in the Poison section below.)

A paralyzed character cannot move, speak, or take any physical action. He is rooted to the spot, frozen and helpless. Not even friends can move his limbs. He may take purely mental actions, such as casting a spell with no components.

A winged creature flying in the air at the time that it becomes paralyzed cannot flap its wings and falls. A swimmer can't swim and may drown.

When a character takes damage from an attack with a poisoned weapon, touches an item smeared with contact poison, consumes poisoned food or drink, or is otherwise poisoned, he must make a Fortitude saving throw. If he fails, he takes the poison's initial damage (usually ability damage). Even if he succeeds, he typically faces more damage 1 minute later, which he can also avoid with a successful Fortitude saving throw.

One dose of poison smeared on a weapon or some other object affects just a single target. A poisoned weapon or object retains its venom until the weapon scores a hit or the object is touched (unless the poison is wiped off before a target comes in contact with it). Any poison smeared on an object or exposed to the elements in any way remains potent until it is touched or used.

Although supernatural and spell-like poisons are possible, poisonous effects are almost always extraordinary.

Poisons can be divided into four basic types according to the method by which their effect is delivered, as follows.

Magic can cause creatures and characters to change their shapes-sometimes against their will, but usually to gain an advantage. Polymorphed creatures retain their own minds but have new physical forms.

The polymorph spell defines the general polymorph effect.

Since creatures do not change types, a slaying or bane weapon designed to kill or harm creatures of a specific type affects those creatures even if they are polymorphed. Likewise, a creature polymorphed into the form of a creature of a different type is not subject to slaying and bane effects directed at that type of creature.

A ranger's favored enemy bonus is based on knowing what the foe is, so if a creature that is a ranger's favored enemy polymorphs into another form, the ranger is denied his bonus.

A dwarf's bonus for fighting giants is based on shape and size, so he does not gain a bonus against a giant polymorphed into something else, but does gain the bonus against any creature polymorphed into a giant.

Telepathy, mental combat and psychic powers-psionics is a catchall word that describes special mental abilities possessed by various creatures. These are spell-like abilities that a creature generates from the power of its mind alone-no other outside magical force or ritual is needed. Each psionic creature's description contains details on its psionic abilities.

Psionic attacks almost always allow Will saving throws to resist them. However, not all psionic attacks are mental attacks. Some psionic abilities allow the psionic creature to reshape its own body, heal its wounds, or teleport great distances. Some psionic creatures can see into the future, the past, and the present (in far-off locales) as well as read the minds of others.

All ray attacks require the attacker to make a successful ranged touch attack against the target. Rays have varying ranges, which are simple maximums. A ray's attack roll never takes a range penalty. Even if a ray hits, it usually allows the target to make a saving throw (Fortitude or Will). Rays never allow a Reflex saving throw, but if a character's Dexterity bonus to AC is high, it might be hard to hit her with the ray in the first place.

Creatures with this extraordinary ability recover from wounds quickly and can even regrow or reattach severed body parts. Damage dealt to the creature is treated as nonlethal damage, and the creature automatically cures itself of nonlethal damage at a fixed rate.

Certain attack forms, typically fire and acid, deal damage to the creature normally; that sort of damage doesn't convert to nonlethal damage and so doesn't go away. The creature's description includes the details.

Creatures with regeneration can regrow lost portions of their bodies and can reattach severed limbs or body parts. Severed parts die if they are not reattached.

Regeneration does not restore hit points lost from starvation, thirst, or suffocation.

Attack forms that don't deal hit point damage ignore regeneration.

An attack that can cause instant death only threatens the creature with death if it is delivered by weapons that deal it lethal damage.

A creature with resistance to energy has the ability (usually extraordinary) to ignore some damage of a certain type each round, but it does not have total immunity.

Each resistance ability is defined by what energy type it resists and how many points of damage are resisted. It doesn't matter whether the damage has a mundane or magical source.

When resistance completely negates the damage from an energy attack, the attack does not disrupt a spell. This resistance does not stack with the resistance that a spell might provide.

This extraordinary ability lets a creature detect approaching enemies, sniff out hidden foes, and track by sense of smell.

A creature with the scent ability can detect opponents by sense of smell, generally within 30 feet. If the opponent is upwind, the range is 60 feet. If it is downwind, the range is 15 feet. Strong scents, such as smoke or rotting garbage, can be detected at twice the ranges noted above. Overpowering scents, such as skunk musk or troglodyte stench, can be detected at three times these ranges.

The creature detects another creature's presence but not its specific location. Noting the direction of the scent is a move action. If it moves within 5 feet of the scent's source, the creature can pinpoint that source.

A creature with the Track feat and the scent ability can follow tracks by smell, making a Wisdom check to find or follow a track. The typical DC for a fresh trail is 10. The DC increases or decreases depending on how strong the quarry's odor is, the number of creatures, and the age of the trail. For each hour that the trail is cold, the DC increases by 2. The ability otherwise follows the rules for the Track feat. Creatures tracking by scent ignore the effects of surface conditions and poor visibility.

Creatures with the scent ability can identify familiar odors just as humans do familiar sights.

Water, particularly running water, ruins a trail for air-breathing creatures. Water-breathing creatures that have the scent ability, however, can use it in the water easily.

False, powerful odors can easily mask other scents. The presence of such an odor completely spoils the ability to properly detect or identify creatures, and the base Survival DC to track becomes 20 rather than 10.

Spell resistance is the extraordinary ability to avoid being affected by spells. (Some spells also grant spell resistance.)

To affect a creature that has spell resistance, a spellcaster must make a caster level check (1d20 + caster level) at least equal to the creature's spell resistance. (The defender's spell resistance is like an Armor Class against magical attacks.) If the caster fails the check, the spell doesn't affect the creature. The possessor does not have to do anything special to use spell resistance. The creature need not even be aware of the threat for its spell resistance to operate.

Only spells and spell-like abilities are subject to spell resistance. Extraordinary and supernatural abilities (including enhancement bonuses on magic weapons) are not. A creature can have some abilities that are subject to spell resistance and some that are not. Even some spells ignore spell resistance; see When Spell Resistance Applies, below.

A creature can voluntarily lower its spell resistance. Doing so is a standard action that does not provoke an attack of opportunity. Once a creature lowers its resistance, it remains down until the creature's next turn. At the beginning of the creature's next turn, the creature's spell resistance automatically returns unless the creature intentionally keeps it down (also a standard action that does not provoke an attack of opportunity).

A creature's spell resistance never interferes with its own spells, items, or abilities.

A creature with spell resistance cannot impart this power to others by touching them or standing in their midst. Only the rarest of creatures and a few magic items have the ability to bestow spell resistance upon another.

Spell resistance does not stack. It overlaps.

A creature with tremorsense automatically senses the location of anything that is in contact with the ground and within range.

If no straight path exists through the ground from the creature to those that it's sensing, then the range defines the maximum distance of the shortest indirect path. It must itself be in contact with the ground, and the creatures must be moving.

As long as the other creatures are taking physical actions, including casting spells with somatic components, they're considered moving; they don't have to move from place to place for a creature with tremorsense to detect them.

Some creatures (usually undead) are less easily affected by the turning ability of clerics or paladins.

Turn resistance is an extraordinary ability.

When resolving a turn, rebuke, command, or bolster attempt, added the appropriate bonus to the creature's Hit Dice total.