Elaborate Firecannon

A colorless repeatable Shock at this cost would sit far above rate, so the whole apparatus exists to keep the gun from firing cleanly turn after turn. It stays down after every shot, and the only reliable way to bring it back online is a discard at the start of your upkeep: the cardboard you feed it is the real activation cost, not just the four mana the ability charges. Stacked together (four mana, a card, plus the tap), the price per ping runs enormous, which is why this grinds rather than removes. That discard-to-untap clause is the tell about who it was built for: a deck already churning its library, one that treats the graveyard as a resource and would happily pitch dead draws it has no use for anyway. Note the timing wrinkle, though. The cannon fires whenever it is untapped, so the first shot off the top is free of any discard, and any outside untap effect resets it without touching your hand: the discard is only the cost of keeping it firing repeatedly. Pull it out of a self-mill or madness-adjacent shell and the math collapses; an artifact that wants a card every turn to deal two is too expensive to anchor a removal plan on its own. Inside the right engine, it turns a stream of otherwise wasted cards into instant-speed two-point bursts, picking off small creatures, a wounded planeswalker, or a player near the bottom of their clock.