Casting Time 1 standard action
Components V, S
If the attacking undead’s Hit Dice is less than or equal to your caster level, the blood drain or energy drain has no effect. If the attacking undead’s Hit Dice are greater than your caster level, the undead must make a Fortitude save (against the DC of the spell) with each attack for those special abilities to have any effect. The spell only prevents the Constitution damage from blood drain and negative levels from energy drain, but not any other effects of these attacks.
Pathfinder Roleplaying Game Advanced Race Guide © 2012, Paizo Publishing, LLC; Authors: Dennis Baker, Jesse Benner, Benjamin Bruck, Jason Bulmahn, Adam Daigle, Jim Groves, Tim Hitchcock, Hal MacLean, Jason Nelson, Stephen Radney-MacFarland, Owen K.C. Stephens, Todd Stewart, and Russ Taylor.