He is the head of Angart family and is involved in the administration of Midhaze. Zerceus is the head of the Angart family and the second most powerful demon in Midhaze, after Demon Lord Elio. He played a part in Midhaze's administration, as he attended all the meetings to discuss new policies, and his opinions were always valuable. He was known for promoting harsher policies on royalty, but this would revealed to be a cover for his true beliefs. After the segregation of royal and mixed-blood demons was abolished, Zerceus formed the Resistance, a covert group that disapproves of Midhaze's new decree and clings to its old ways of royal supremacy. As such, he dismisses Demon King Anos as a fake that was planted by the Unitarians.

(Source: Maou Gakuin Wiki)