I managed to kill my own lord with life magic.

These are 2 sister lords who spent about 50 turns total waiting in towns to get all the Stance traits, Sister Sword trait, Helm of Draesca trait and the Clownfather Nurgle trait. One is a death mage and the other is a life mage, and they go around the world as a team murdering everything.

Apparently that murder also includes each other because Awakening of the Woods knocked one mage from the wall into the tower, killing her instantly.