Scoria Wurm

The coin flip is the design honesty here. A 7/7 for five mana was, in its era, a body well above curve, the kind of beater that ends games in three swings. Wizards priced that aggression by attaching a tax that recurs every turn you keep the thing alive: each upkeep, half the time, the Wurm packs up and goes home. The asymmetry is the whole point. You pay the five mana once, but the variance compounds, so the longer the game runs the more likely you have to recast it, and recasting eats another turn of tempo you wanted to spend attacking. It is randomized maintenance dressed up as a creature, a cousin to the old upkeep-tax designs (Juggernaut had to attack, Lord of the Pit demanded a sacrifice) except the cost here is pure chance rather than a predictable obligation. That makes it almost impossible to plan around: you cannot sequence to dodge the flip, only hope to win it, which is exactly why a stat line this generous was allowed to exist for one red and four generic. The flip also creates a strange loop with cards that want creatures bouncing or re-entering play, and any way to skip upkeeps at all turns the drawback off entirely. Left to its own devices, though, it is a clean expression of high-roll design: enormous when it stays, a five-mana feel-bad when the coin betrays you.