Tear of the Archon:

At the start of a war session, the wielder of the Tear of the Archon may spend 1 nation magic point to instantly take control of any non-ruler/archon Void unit. Only one unit can be taken at a time. Additionally, at the start of any war session, the wielder of the Tear of Archon may designate one friendly unit to become a Void Archon under their control. Only one Void Archon may exist in a war at a time. At the end of a war session, there is a 5% chance the Void Archon becomes a hostile unit. Each time this unit attacks, substitutes its attack, or joins a battle, this chance increases by 5%. Before the chance is rolled, the user choose to sacrifice 2 Nation Magic to reduce the chance by 10%.