the silent monks fighting with Kniles Flenser explode when they die and because you had enrage, you received a lot of damage.
This is the reason. You were enraged -100% resist all. So you take double damage from all magic/surfaces. You killed the monk with poison type weapon which creates a poison surface. The monk dies and explodes causing high damage to you, then causes a secondary explosion with the poison surface which causes more damage to you, all the while you are taking double damage from everything. So you basically committed suicide by enraged hugging.
