Needs review
Source: Player's Handbook II

Description: Spend spell slot to gain hit points equal to level spent.

Prerequisites: Toughness, 3rd Level Caster (arcane)

Required for: Arcane Consumption

You can expend a prepared spell or spell slot as an immediate action when you are reduced to 0 or fewer hit points. You heal a number of points of damage equal to the level of the spell or spell slot used in this manner. You cannot use this ability to negate effects that disable you without causing hit point damage, such as a medusa's ability to turn you to stone. Even if this healing does not bring you above negative hit points, it still stabilizes you. Using a 0-level spell with this feat grants no benefit.