Shadowform

Assume Shadowform, increasing your Shadow damage by 10%, reducing the Mana cost of all Shadow spells by 50%, increasing the critical strike damage bonus of your Shadow spells by 100%, and reducing Physical damage taken by you by 15%. However, you may not cast healing spells while in this form.

Aura: Shadow damage you deal increased by 10%. Mana cost of all Shadow spells reduced by 50%. Critical strike damage bonus of Shadow spells increased by 100%. Physical damage you take reduced by 15%. You may not cast healing spells.