Constrict: When a creature with the constrict universal monster rule (Bestiary, page 298) grapples a foe, when does it deal constrict damage?
A creature with constrict deals this additional damage every time it makes a successful grapple check against a foe. This includes the first check to establish the grapple (such as when using the grab universal monster rule).
How does DR interact with magical effects that deal bludgeoning, piercing, or slashing damage?
Although the Bestiary definition of Damage Reduction (page 299) says "The creature takes normal damage from energy attacks (even nonmagical ones), spells, spell-like abilities, and supernatural abilities," that's actually just referring to damage that isn't specifically called out as being of a particular type, such as fire damage or piercing damage. In other words, DR doesn't protect against "typeless damage" from magical attacks.
However, if a magical attack specifically mentions that it deals bludgeoning, piercing, or slashing damage, DR affects that damage normally, as if it were from a physical weapon. (Otherwise the magical attack might as well not have a damage type, as it would only interface with B/P/S damage in a very few corner cases, such as whether or not an ooze splits from that attack.)
For example, the ice storm spell deals 3d6 points of bludgeoning damage and 2d6 points of cold damage. If you cast ice storm at a group of zombies, the zombie's DR 5/slashing protects them against 5 points of the spell's bludgeoning damage. Their DR doesn't help them against the spell's cold damage because DR doesn't apply to energy attacks.
Negative Energy Affinity: How is this ability (Bestiary 2, page 299) supposed to work?
The intent of this ability is that the creature is healed by negative energy (like an undead) and harmed by positive energy (like an undead); this is automatic and has nothing to do with the intent of the target or the energy-wielder. However, as written, the ability is a bit confusing because of the phrase “reacts to,” which doesn’t have a clear definition. This ability will be changed in the next printing of Bestiary 2.
Update: Page 299—In the description of the Negative Energy Affinity ability, replace the current entry with the following:
Negative Energy Affinity (Ex) The creature is alive, but is treated as undead for all effects that affect undead differently than living creatures, such as cure spells and channeled energy. Format: negative energy affinity; Location: Defensive Abilities.
Grab: The grab rules for the Bestiary say the ability only works on creatures smaller than the monster, but the grab rules for Bestiary 2 say the ability works on creatures of up to the monster's own size. Which is correct?
Bestiary 2 is the new, updated version: grab works on creatures up to the size of the monster with the grab ability. The next time we do a reprint of the original Bestiary, we'll update all references to grab and similar abilities to reflect this change.
Pounce: If have this ability (page 302), can I make iterative attacks with weapons as part of my full attack?
Any melee attack sequence you can perform as a full attack is allowed as part of the charge-pounce-full attack. For example, a barbarian with the greater beast totem rage power gains the pounce universal monster ability and could make iterative attacks with manufactured melee weapons as part of her charge-pounce-full attack.
Swallow Whole: Once you've dealt enough damage to a monster's insides, what kind of action is it to escape?
A swallowed character must use a standard action, move action, or 5-foot-step to escape. This applies whether the acting character is the one who cut his way free or another swallowed character making use the exit carved by another character.
Vampire: Does a ranger with favored enemy: humanoid (human) get his favored enemy bonus against a human-turned-vampire?
No. According to the vampire template, a human-turned-vampire doesn't keep the (human) subtype, so the ranger's bonus doesn't apply—the vampire isn't quite human enough anymore. In general, favored enemy: humanoid isn't effective against a creature that is a type other than humanoid (such as a vampire, which is type: undead).
Change Shape: Does a creature with this ability use the duration of the change shape spell, and have to keep renewing as it expires?
As originally written, with how the Pathfinder rules for change shape work, a creature with the ability must keep renewing it every few minutes, as it is based on a spell with a duration. This negatively affects creatures such as doppelgangers, which live for extended periods in an alternate form, and having to reactivate this ability would ruin the ruse, especially as it couldn't do so while it slept.
The way this ability works is being updated as of Bestiary 2. For now, unless a creature's description says otherwise, treat any creature with change shape as if it had the ability to remain in its alternate form indefinitely, without needing to reactivate the ability. (SKR 9/23/10)