Immersive Experience

Immersive Experience can be equipped to creatures you don't control and may be equipped whenever you could cast an instant.
Equip — {1}{b/r}{w/u}, Discard a card
Equipped creature can't attack, block, crew, or have its abilities activated unless the current game is a subgame and has "At the beginning of your upkeep, put a +1/+1 counter on this creature, then mill cards equal to its power."