You change the subject into a Small or smaller animal (including magical beast type) of no more than 1 HD. If the form the subject would assume has any of the following abilities, they gain the listed ability: burrow 30 feet, climb 90 feet, fly 90 feet (good maneuverability), swim 90 feet, blindsense 30 feet, darkvision 60 feet, low-light vision, scent, constrict, ferocity, grab, jet, poison, pounce, rake, trample, trip, and web.

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

Tiny animal: If the form you take is that of a Tiny animal, you gain a +4 size bonus to your Dexterity, a –2 penalty to your Strength, and a +1 natural armor bonus.

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

Small magical beast: If the form you take is that of a Small magical beast, you gain a +4 size bonus to your Dexterity, and a +2 natural armor bonus.

If the new form would prove fatal to the creature, such as an aquatic creature not in water, the subject gets a +4 bonus on the save.

If the spell succeeds, the subject must also make a Will save. If this second save fails, the creature loses its extraordinary, supernatural, and spell-like abilities, loses its ability to cast spells (if it had the ability), and gains the alignment, special abilities, and Intelligence, Wisdom, and Charisma scores of its new form in place of its own. It still retains its class and level (or HD), as well as all benefits deriving therefrom (such as base attack bonus, base save bonuses, and hit points). It retains any class features (other than spellcasting) that aren't extraordinary, supernatural, or spell-like abilities.

Small magical beast: If the form you take is that of a Small magical beast, you gain a +4 size bonus to your Dexterity, and a +2 natural armor bonus.

Any polymorph effects on the target are automatically dispelled when a target fails to resist the effects of baleful polymorph, and as long as baleful polymorph remains in effect, the target cannot use other polymorph spells or effects to assume a new form. Incorporeal or gaseous creatures are immune to baleful polymorph, and a creature with the shapechanger subtype can revert to its natural form as a standard action.