When you cast this spell, you can assume the form of any Diminutive, Tiny, Small, Medium, Large or Huge corporeal Creature of the Undead type, which must be vaguely humanoid-shaped (like a ghoul, skeleton, or zombie). If the form you assume has any of the following abilities, you gain the listed ability: Burrow 60 feet, climb 90 feet, fly 120 feet (good maneuverability), swim 120 feet, Blindsense 60 feet, Darkvision 90 feet, Lifesense 60 feet, low-light Vision, scent, Tremorsense 60 feet, Breath Weapon, Constrict, DR 10/magic and silver, DR 15/bludgeoning and magic, fast Healing 5, fiery death, fire aura, grab, Incorporeal, jet, Poison, Pounce, rake, rend, roar, spikes, Trample, trip, and web.

In this form, you detect as an Undead Creature (such as with detect Undead, but not with magic that reveals your True Form, such as True Seeing) and are treated as Undead for the purposes of channeled energy, cure spells, and inflict spells, but not for other effects that specifically target or react differently to Undead (such as Searing Light).

In this form, you gain a +4 bonus on saves against mind-affecting effects, Disease, Poison, sleep, and stunning. If the form has a vulnerability to an attack (such as sunlight), you gain that vulnerability.

If the Creature has Immunity or Resistance to any energy types, you gain Resistance 20 to those energy types. If the Creature has vulnerability to an energy type, you gain that vulnerability. In this form, you gain a +8 bonus on saves against mind-affecting effects, Disease, Poison, sleep, and stunning. If the form has a vulnerability to an attack (such as sunlight), you gain that vulnerability.

If the creature's form is Incorporeal, the spell's Duration is in rounds per level instead of minutes per level, and your bite and claw (or slam) attacks are Incorporeal touch attacks. If the Creature has Immunity or Resistance to any energy types, you gain Resistance 30 to those energy types. If the Creature has vulnerability to an energy type, you gain that vulnerability. In this form, you gain a +8 bonus on saves against mind-affecting effects, Disease, Poison, sleep, and stunning. If the form has a vulnerability to an attack (such as sunlight), you gain that vulnerability.

Diminutive Undead: If the form you take is that of a Diminutive Undead, you gain a +6 size bonus to your Dexterity, a –4 Penalty to your Strength, and a +1 natural armor bonus.

Tiny Undead: If the form you take is that of a Tiny Undead, you gain a –2 Penalty to your Strength, a +8 size bonus to your Dexterity, and a +3 natural armor bonus.

Small Undead: If the form you take is that of a Small Undead, you gain a +2 size bonus to your Dexterity and a +1 natural armor bonus.

Medium Undead: If the form you take is that of a Medium Undead, you gain a +2 size bonus to your Strength and a +2 natural armor bonus.

Large Undead: If the form you take is that of a Large Undead, you gain a +6 size bonus to your Strength, a –2 Penalty on your Dexterity, a +2 size bonus to your Constitution, and a +6 natural armor bonus.

Huge Undead: If the form you take is that of a Huge Undead, you gain a +6 size bonus to your Strength, a –4 Penalty to your Dexterity, and a +6 natural armor bonus.