Captain Rex Nebula (Showcase)

At the beginning of combat on your turn, target nonland permanent you control becomes a Vehicle artifact until end of turn. Its base power and toughness are each equal to its mana value. It has crew 2 and "Crash Land — Whenever this Vehicle deals damage, roll a six-sided die. If the result is equal to this Vehicle's mana value, it deals that much damage to any target, then sacrifice this Vehicle."