Mystic CompassHow it works & interactions with other cards

Changing the Terrain

When you activate Mystic Compass, you choose a target land and a basic land type: Plains, Island, Swamp, Mountain, or Forest. The targeted land loses all its previous land types and any existing abilities, gaining the new basic land type and its corresponding mana-producing ability. Note that it keeps its name and its supertypes, such as Legendary or Snow, but it will only tap for the color of mana associated with the chosen type.

Step-by-Step Resolution

First, pay one mana and tap Mystic Compass to put the ability on the stack, choosing a target land. Second, as the ability resolves, you choose the basic land type. Third, the land's subtypes are replaced; for example, if you choose Mountain, the land is now a Mountain and can tap for Red mana. This effect lasts until the end of the current turn, at which point the land reverts to its original printed state.

Strategic Considerations

A common mistake is thinking the land retains its original abilities. If you turn a utility land into a Forest, it can no longer use its unique non-mana abilities. Furthermore, this effect can be used defensively to 'turn off' an opponent's color fixing or offensively to grant your creatures landwalk abilities. It is most effective when used during an opponent's upkeep to deny them access to a specific color of mana for their main phase.

Interaction examples

Fixing Your Colors

Sol Ring

If you have a Sol Ring but need colored mana to cast a spell, you can tap Sol Ring for two colorless mana. Use one of that mana to activate Mystic Compass, targeting a land you control (like a Wastes). Choose 'Island' as the type. Your land is now an Island and can be tapped for the Blue mana you were missing.

Managing Commander Identity

Arcane Signet

In a scenario where an opponent controls a land that provides a color you need to interact with, but your Arcane Signet is limited by your Commander's identity, you can use Mystic Compass to change your own basic land. If you turn a Plains into a Swamp using the Compass, you ensure you have the correct type for effects that check for Swamps, even if your Signet cannot produce Black mana.