Spell Power

From DDO Compendium

Spell Power is an attribute of Dungeons & Dragons Online that enhances the damage of your damaging spells or spell effects

Typically, 1 spell power = 1% more damage with spells of that type

Positive and Negative Energy Spell Power typically only benefit from 50% Spell Power, such that 1 spell power = 0.5% damage or healing from Positive or Negative Spells