You burn your life force to strengthen your spells.
BENEFIT
While casting a spell, you can increase your effective caster level by one, but in so doing you take 1d8 points of non-elemental damage and non-lethal damage each. At 8th level, you can choose to increase your effective caster level by two, but you take 3d8 points of non-elemental damage and non-lethal damage each. At 15th level, you can increase your effective caster level by three, but you take 5d8 points of non-elemental damage and non-lethal damage each. The effective increase in caster level increases all caster level-dependent effects, such as range, duration, and overcoming spell resistance, but not spendable MP.