Good ideas. Probably not dispel evil, though, since these are neutral. What if we say any lethal damage causes it to let go? And if freedom of movement works, so should a grapple check. Revising:
Immunity to Magic (Ex): A lich's blood is immune to any spell or spell-like ability that allows spell resistance. In addition, certain spells and effects function differently against the creature, as noted below. Dispel magic or greater dispel magic cast on a lich's blood does 1d6 hp of normal damage per caster level, and antimagic field destroys a lich's blood (on a failed Fort save).
The One that Coats is the Only One You Need (Su): On a successful grapple check against an arcane spellcaster, a lich's blood streams into its victims orifices, coating its nostrils and lungs and making it impossible to breathe (see the DMG for suffocation rules). Each round, the victim must make a DC X Will save or lose its highest level prepared spell or spell slot. When the victim has no remaining spells or spell slots, the lich's blood remains for five more rounds, dealing a negative level each round on a failed save (if the victim is still alive).
Once a lich's blood has coated a spellcaster, the victim may escape by making two successful grapple or Escape Artist checks (as if to escape a pin). A freedom of movement spell cast on the victim also immediately causes the lich's blood to retract. In addition, if the lich's blood takes X hit points of normal damage, it will retract. Any weapon attacks directed at the lich's blood while it is coating a victim deal 1/2 of their damage to the victim instead.
