Arcane Heist

The exiled card with cipher grants a triggered ability to the creature it’s encoded on. If that creature loses that ability and subsequently deals combat damage to a player, the triggered ability won’t trigger. However, the exiled card will continue to be encoded on that creature.

If the spell you cast has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.

You choose whether to cast the target instant or sorcery card as Arcane Heist resolves. If you do, you do so as part of the resolution of Arcane Heist. You can’t wait to cast it later in the turn. Timing restrictions based on the card’s types are ignored.

You cast the copy of the card with cipher during the resolution of the triggered ability. Ignore timing restrictions based on the card’s type.

If a creature with an encoded card deals combat damage to more than one player simultaneously (perhaps because some of the combat damage was redirected), the triggered ability will trigger once for each player it deals combat damage to. Each ability will create a copy of the exiled card and allow you to cast it.

The spell with cipher is encoded on the creature as part of that spell’s resolution, just after the spell’s other effects. That card goes directly from the stack to exile. It never goes to the graveyard.