SRD:Energy Drained

Energy Drained
The character gains one or more negative levels, which might permanently drain the character’s levels. If the subject has at least as many negative levels as Hit Dice, he dies. Each negative level gives a creature the following penalties: –1 penalty on attack rolls, saving throws, skill checks, ability checks; loss of 5 hit points; and –1 to effective level (for determining the power, duration, DC, and other details of spells or special abilities). In addition, a spellcaster loses one spell or spell slot from the highest spell level castable.