Migratory GreathornHow it works & interactions with other cards

What It Does

Migratory Greathorn features the Mutate keyword, allowing you to cast it for a reduced cost of {2}{G} if you target a non-Human creature you own. When it resolves, it merges with the target into a single permanent that has the power, toughness, and types of the card on top, plus all the abilities of every card in the stack. Crucially, its triggered ability fires not just when it first mutates, but every single time a new mutation is added to that creature stack.

How It Resolves Step by Step

First, you choose to cast the spell for its Mutate cost and select a legal target, like a non-Human creature. Upon resolution, you decide whether to place Migratory Greathorn on top of or underneath the target. The 'Whenever this creature mutates' ability then triggers. You search your library for a basic land card, put it onto the battlefield tapped, and then shuffle your library. If the creature stack is ever removed from the battlefield, all cards in the stack go to the appropriate zone, such as the graveyard.

Common Mistakes

A frequent error is trying to mutate Migratory Greathorn onto a Human; the ability specifically requires a non-Human target. Another mistake involves timing: if the target creature is destroyed in response to the Mutate spell, Migratory Greathorn still resolves, but it enters the battlefield as a normal creature instead of mutating. Remember that the land entered via the triggered ability always enters tapped, so you cannot use that mana immediately.

When to Play It

Play Migratory Greathorn early in the game to jump from three mana to five, setting up your late-game threats. Because the ability triggers every time the creature mutates, it is highly effective to keep piling more Mutate cards onto the same stack to repeatedly trigger the land-searching effect. It is best used on creatures that already have protective keywords like Hexproof or Indestructible to ensure your investment stays on the board.

Interaction examples

Scaling the Ramp

Solemn Simulacrum

If you have Solemn Simulacrum on the battlefield and cast Migratory Greathorn for its Mutate cost targeting the Golem, you will search for a basic land when the mutation resolves. The resulting permanent is a single creature with the land-searching ability of the Greathorn and the 'draw a card' death trigger of the Simulacrum. If that stack dies, you still draw a card because the merged permanent possessed that ability.

Targeting Restrictions

Eternal Witness

You cannot cast Migratory Greathorn for its Mutate cost targeting Eternal Witness. This is because Eternal Witness has the 'Human' creature type. If you want to play Migratory Greathorn in this scenario, you must cast it for its full cost of {3}{G} as a separate creature, and you will not receive the search trigger because no mutation occurred.

Solo Efficiency

If you have no other creatures, you can cast Migratory Greathorn for its standard mana cost of {3}{G}. It enters the battlefield as a 3/4 Beast. While it won't trigger its land-search ability immediately, it remains on the battlefield as a valid mutation target for future Mutate spells, which would then trigger the Greathorn's ability to fetch a land.