Shivan Wurm

Seven power, seven toughness, and trample for five mana is a body that should have cost far more by the standards of its era; the entry trigger is the bill that comes due. Sending one of your own red or green creatures back to your hand isn't a downside the card tolerates so much as a hook it dangles: hand it the worst body you have and the tax is nearly free, or hand it your best enters-the-battlefield creature and convert the cost into an engine. That second reading is why the design persists. Loop it with a permanent whose arrival does real work, recast both each turn, and the mandatory recursion becomes a way to fire that trigger again and again. The card heads a cycle of oversized two-color creatures that each send a permanent home on entry, and this one is the cleanest member because trample on a 7/7 closes games even when there's nothing clever to recur. The tension Wizards built in is timing: the trigger fires on entry and is not optional, so a turn where the only red or green creature you control is the Wurm itself bounces it right back, undoing the play entirely. Sequencing around that requirement, landing a sacrificial body before the Wurm arrives, is the small puzzle that separates the card from a pure beater.