Spell Power

Spell power rating determines how much damage you deal with spells. In most cases, each point of spell power increase increases the base damage of your spell by 1 %. Various effects can contribute to your spell power, all effects are added together.

Spell power was introduced in Update 14 and replaced previous spell damage amplification that involved addition and multiplication.

This concept applies only to spells that cause hit point damage and spells that heal hit points.

Sources of spell power:
 * Enhancements, e.g. Cleric Life Magic or Sorcerer Fire Manipulation
 * Metamagic feats (spell power increases from metamagic feats stack)
 * Empower Healing Spell +75
 * Empower Spell +75
 * Maximize Spell +150
 * Magic items
 * Equipment bonus from items with enchantments like Potency or Combustion
 * Implement bonus from caster weapons (equal to 3 * enhancement bonus of the weapon)
 * Alchemical bonus from clickies, e.g. Inferno
 * Psionic bonus from Xachosian Eardweller

Some spells receive limited (usually half) benefit from spell power:
 * Heal: 50%
 * Mass Heal: 50%
 * Necrotic Touch (Pale Master): 50%
 * Necrotic Bolt (Pale Master): 50%
 * Necrotic Blast (Pale Master): 50%
 * Arcane Bolt (Archmage): 50%
 * Arcane Blast (Archmage): 50%
 * Summon Archon (Favored Soul): 50%
 * All Runearm Shots: Between 50% and 80%

Heal and Mass Heal spells still receive full benefit from the Empower Healing Spell feat.

Dev explanation: