Spell vamp

Spell vamp is a magic stat that works as a counterpart of life steal. However, instead of regenerating health based on basic attacks, the regeneration of health is based on damage done by champion abilities. It works off of activated item effects, summoner spells, and abilities, regardless of the type of damage done. Spell vamp is calculated from the damage dealt to the enemy after reductions such as magic resistance, armor or effects like. See also : list of effects that apply or don't apply spell vamp.

Champion abilities

 * grants 35% spell vamp for the next spell upon reaching 9 charges of Essence Theft.
 * grants 8% spell vamp when she obtains 10 bonus attack damage, increasing by an additional 1% for every 6 bonus attack damage gained thereafter.
 * grants spell vamp.
 * grants spell vamp.
 * increases his damage based on his health and grants him life steal and spell vamp for 6 seconds.
 * grants spell vamp.
 * has a natural 100% spell vamp
 * has a natural 100% spell vamp

Masteries

 * grants spell vamp.

Runes

 * Quintessences of grant  spell vamp.

Calculations
The amount of health restored with Spell Vamp follows the following formula:
 * Health restoredtotal spell damagespell vampvamp coefficient

where
 * Total spell damage is the the mitigated spell damage done to every target affected, and
 * Vamp coefficient is 1 for single target spells and 1/3 for multi-target spells.

Examples
Assuming targets with 0 pertinent resistance (armor for physical damage or magic resistance for magic damage):
 * 25% spell vamp on a single-target spell that does 100 damage will return 1000.25125 health.
 * 25% spell vamp on an AoE spell that does 100 AoE damage to each of 4 targets will return 41000.25(13)33.3 health.

Trivia
The greatest spellvamp currently possible is 200% on.

This requires:
 * Attack Damage sources
 * 200 AD - 2 x (fully stacked)
 * 110 AD - (fully stacked)
 * 40 AD -
 * 40 AD -
 * 10 AD -
 * 8 AD - nearby (aura)
 * 23 AD -
 * 50 AD -
 * 20 AD -
 * 35 AD -
 * 5 AD - with
 * 39.25 AD - Marks of, Seals of Might and Glyphs of Might
 * 3 AD -
 * 9 AD -
 * Total AD: 592 AD (note that the first 10AD equates to 8%)
 * Conversion: (592 - 10) / 6 = 97.04%
 * Total: 105.04%


 * Spell Vamp sources
 * 20% -
 * 20% -
 * 20% - nearby allied (aura)
 * 6% - Quintessences of
 * 3% -
 * Total: 69%


 * Improves the subtotal of 174.04% to 174.04 * 1.15 = 200.15%