Ruin Crab

Landfall — Whenever a land you control enters, each opponent mills three cards. (To mill a card, a player puts the top card of their library into their graveyard.)

Hedron Crab

Landfall — Whenever a land you control enters, target player mills three cards.

March of Burgeoning Life

As an additional cost to cast this spell, you may exile any number of green cards from your hand. This spell costs {2} less to cast for each card exiled this way.
Choose target creature with mana value less than X. Search your library for a creature card with the same name as that creature, put it onto the battlefield tapped, then shuffle.