The Skull Stags are Nightmare Skulls born out of Oberon Greenhaze's Nightmares. These Nightmarish deer-like creatures are the shamans of the Skull Tribe, performing unholy rituals to worship their "Father" throughout the forest. They use skull staffs.
Skull stags are also able to resurrect fallen Nightmare Skulls, as long as their corpses are still on the ground, and have not faded away, similar to the Blue Minion healing ability and also can slow down minions. When killed, they drop blue lifeforce and have a chance to drop their skulls, as well as their staffs.