Loop

A loop describes a set of actions that could be repeated indefinitely.

Loops need to produce something per rotation to be useful, such as:

• Infinite mana (Freed from the Real + Axebane Guardian + any defender)
• Infinite tokens (Midnight Guard + Presence of Gond)
• Infinite life
• Infinite damage
• Infinite storm count

Once a rotation is established it might be possible to take shortcuts. The rules for resolving loops are also defined under those for shortcuts.

Loops can't actually run infinitely. If the loop is possible due to the repeated actions of a player, the player must name an actual number of times they will continue the loop before stopping, usually a very large number. If the loop would be infinite due to mandatory actions, the game ends in a draw.

Rules

From the glossary of the Comprehensive Rules (June 7, 2024—Modern Horizons 3)

Loop

A set of actions that could be repeated indefinitely. See rule 729, “Taking Shortcuts.”