Majora's Mask

(As an Item becomes attached to a creature, unattach from that creature all other Items attached to it.)
{r}{w}{u}, {t}: At the beginning of the first upkeep after your next turn, exile all other permanents and Majora's Mask deals 10 damage to each player. Activate this ability only if equipped creature dealt combat damage to a player this turn.
Equip {x} - X is the number of creatures you control.