Coriantumr, Last of All

Partner with Ether, Witness of the End

When Coriantumr enters, return Ether to the command zone from anywhere (this does not affect commander tax)

Menace, Weapons of War 3

You don't lose the game for having 0 or less life.

At the beginning of your upkeep, you lose seven life. When you do, if your life total is less than half your starting life total, put a -1/-1 counter on Coriantumr.