Power Infusion

Power Infusion is a level 100 Discipline and level 90 Shadow priest talent. It increases the priest's spell casting speed by 25%, and reduces either mana cost or increases Insanity generation for 20 seconds.

Trivia

 * Power Infusion was once a Discipline-exclusive spell which could be applied to a friendly target, or hoarded by the priest in question, and came with a number of restrictions:
 * Did not stack with Arcane Power. If Arcane Power was already active, a priest casting Power Infusion would receive an error message "A more powerful spell is already active." If Power Infusion was already active on the mage, activating Arcane Power would override it.
 * Did not not stack with Bloodlust/Heroism/Time Warp, or other haste effects which could be applied to others.