Hedrons perplex minds both great and small.

Hedron Crab

Landfall — Whenever a land you control enters, target player mills three cards. (They put the top three cards of their library into their graveyard.)

Landfall — Whenever a land enters the battlefield under your control, target player puts the top three cards of his or her library into his or her graveyard.

Tarkir: Dragonstorm Commander

Some of Zendikar's oddest creatures, hedron crabs decorate their shells with the most peculiar materials.