Your knowledge of the undead makes you especially effective when fighting them.
Prerequisites
Favored enemy (plant) ability.
Benefit
You gain a bonus equal to half your favored enemy (undead) bonus on saving throws against ability damage, ability drain, energy drain, and negative energy effects.
Once per day, when an undead creature’s attack against you deals either ability damage or ability drain or bestows 1 or more negative levels, you can negate the damage, drain, or negative levels as an immediate action.