MTG Keyword Rules — Comprehensive Rules Glossary

Cipher appears on some instants and sorceries. It represents two abilities. The first is a spell ability that functions while the spell with cipher is on the stack. The second is a static ability that functions while the card with cipher is in the exile zone. “Cipher” means “If this spell is represented by a card, you may exile this card encoded on a creature you control” and “For as long as this card is encoded on that creature, that creature has ‘Whenever this creature deals combat damage to a player, you may copy the encoded card and you may cast the copy without paying its mana cost.’”

The term “encoded” describes the relationship between the card with cipher while in the exile zone and the creature chosen when the spell represented by that card resolves.

The card with cipher remains encoded on the chosen creature as long as the card with cipher remains exiled and the creature remains on the battlefield. The card remains encoded on that object even if it changes controller or stops being a creature, as long as it remains on the battlefield.