The Cow Queen, Bovine Potentate is a unique Infernal Bovine found only in the Not The Cow Level in Diablo III. She originally only spawned during the anniversary event in May 2015, leading hordes of her murderous cows to battle. As of patch 2.3.0, one may access the level using Kanai's Cube.
In combat, she has Electrified, Orbiter and Thunderstorm affixes. Her Electrified pulses spread from her even without taking damage, in great numbers, while Orbiter and Thunderstorm deal increased damage. At 50% Life or lower, she also gains Illusionist and Vortex affixes, and may summon two Bovines at her side every few seconds.
Visually, she was much larger than other cows in the area.