Demiplane (Continued)

When a creature kills another creature in the Demiplane, the victorious creature returns to the battlefield with a number of +1/+1 counters equal to the slain creature's mana cost. It can't enter this Demiplane or any other for the rest of the game involuntarily. Creatures in the Demiplane must attack each turn if able. When Demiplane leaves the battlefield, all creatures you control are returned to your hand, and all others die. The Demiplane then closes, and can't be re-opened. {1}, {t}: S