Necrotic Empowerment from Libris Mortis (does require a feat) gives temporary HP.
Personal range, 8th level spell, 1 round/level (Persist anyone?).
+8 Enhancement bonus to Dex, Int and Wis, +8 Natural Armor, +5 competence bonus to Fort Saves and 100 temporary HP.
Does have the [Evil] tag though.
Ridiculous spell if you can manage to persist it somehow. Like, for example Vestige metamagic...