MTG Keyword Rules — Comprehensive Rules Glossary

For a player to mill a number of cards, that player puts that many cards from the top of their library into their graveyard.

A player can’t mill a number of cards greater than the number of cards in their library. If given the choice to do so, they can’t choose to take that action. If instructed to do so, they mill as many as possible. Similarly, the player can’t pay a cost that includes milling a number of cards greater than the number of cards in their library.

An effect that refers to a milled card can find that card in the zone it moved to from the library, as long as that zone is a public zone.

Some spells and abilities mill a single card and then ask for information about the milled card. If more than one card is milled due to replacement effects and the effect of a spell or ability asks for information about the milled card, such as a characteristic or mana value, it gets information from each milled card and will get multiple answers. If these answers are used to determine the value of a variable, the sum of the answers is used. If that effect grants a player permission to cast or play “that” card, the permission applies to each of the milled cards. If that effect performs any actions on “the” card, it performs that action on each milled card. If that effect performs any actions on “a” card, the controller of the spell or ability chooses which card is affected.