Lifedrinking Covenant is a 13th level avenger Encounter power that was introduced in the 382nd edition of Dragon (magazine).
Lifedrinking Covenant
Avenger Attack 13
You bind your enemy’s spirit in a pact with the forces of death, promising to send it to the afterlife one way or another.
Ranged 5
Target: One creature
Attack: Wisdom vs. Will
Hit: 3d8 + Wisdom modifier necrotic damage, and until the end of your next turn the target takes 5 necrotic damage for each square it moves.
Effect: If the target is your oath of enmity target, you can roll twice on this attack and use either result.