Ichor Wellspring

A two-mana artifact that draws a card twice: once on the way down, once on the way out. That double trigger is the whole engine, because it turns the card into a counter that artifact-matters decks want to spend rather than keep. Feed it to a sacrifice outlet like Krark-Clan Ironworks and you bank the death draw while the outlet takes the mana; pop it with an artifact-targeting effect such as Shrapnel Blast as fuel and the cantrip comes free on top. It is built to be destroyed, and that inversion sets the card's whole logic upside down from an ordinary draw artifact: most permanents want to survive, while this one is most valuable in the instant it leaves play, so the question is never whether to sacrifice it but how many graveyard payoffs you can stack on the way down. Disciple of the Vault is the classic companion here, draining a life every time the Wellspring hits the yard, so each cycle is a card plus a point of damage. The enters clause keeps it from being dead in hand when you draw it organically, and the put-into-a-graveyard wording catches sacrifice and destruction alike, so any method that sends it to the graveyard triggers it. As fodder it asks for an artifact deck with both a recursion loop and a payoff for cheap permanents cycling through the yard, which is why it reads as filler in a vacuum and as connective tissue inside the right shell.