Arc of Betrayal

Bond two target players (If those two players attack each other, they break the bond. Whenever a Bonded player gains life, the other player gains the same amount. Whenever a bonded player loses life, the other player gains the same amount.)
At the beginning of bonded players' upkeep, gain 2 life

When the bond is broken, destroy Arc of Betrayal, then both players Berserk, and sacrifice two of their permanents