The covenant grows with sacrifices. Sacrifices grant the covenant size, health, and damage amp.

By dragging a unit over the covenant, they are eaten and their traits are absorbed. The covenant gains additional stats for each trait eaten. You may only eat 1 unit after each combat.

The covenant's ability changes with each threshold.
Damage is based on size x ap.

Traits Eaten
(0) - Mana Reave Enemies and Deal Damage
(6) - Mana Reave Enemies, Deal Damage, and Knock Up
(12) - Mana Reave Enemies, Deal Damage, Knockup additionally in a 1 hex area.
(20) - Takedowns also increase stats.
(Almighty - 25) - Entire Board on Cast, Execute enemies at 20% health, at lower star level than you.