If you're not just using him as a bad Aethergeode MinerAethergeode Miner, however, I do really like RexRex
While it costs three mana normally, if the opponent took any damage, you can pay just one red mana for its spectacle cost, which discounts it
(If unsolved, solve at the beginning of your end step.) Solved Sacrifice this Case: Creature cards in your graveyard gain "You may cast this card from your graveyard" until end of turn
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discard 1 random card from your opponent's hand
You could even use a Rishkar's Expertise or Return of the Wildspeaker to draw a ton of cards, helping you find those Voltron pieces even quicker