Vengeance
Vengeance is a Warlock spell in the WoW Forever client.
When activated, this ability temporarily grants you a 30% increase to your maximum health for 20 sec. After the effect expires, the health is lost. Additionally, while in Metamorphosis, Vengeance causes your wings to slow your falling speed.
Data from the WoW Forever client, build 1.60.1.70862, extracted .