Portal Realm Ring

When a creature deals combat damage to an opponent, on an opponent's turn, the creature's controller may search their library for a card with converted mana cost less than or equal to the
damage that creature dealt.
Creatures you control may attack on an
opponent's combat when the opponent declares
combat if you pay {u/r} for them.
Creatures you don't control cannot attack unless
their controller pays {1} for each attacking
creature.