Thrumming Hivepool

Affinity has always been an artifact-count mechanic: the more metal on the table, the cheaper the next piece drops. Retargeting that discount to a creature type instead of artifacts is the wrinkle, and it aims the cost reduction at exactly the board this card wants to grow. A conventional affinity payoff wants artifacts already deployed; this one wants Slivers, and the deck casting it has spent its early turns doing nothing but making them. The static grant is the load-bearing half. Double strike and haste for every Sliver you control is a combat-math multiplier, not a marginal buff: it doubles the damage of a swarm that is already wide by design and lets freshly minted tokens swing the turn they arrive. The upkeep trigger keeps that swarm feeding itself two bodies at a time, so the double-strike grant has more to double every turn it lives. That combination (a discount that scales with the exact board it improves, a token engine that keeps the board scaling, and a global grant that converts width into lethal damage) is why it reads as an artifact rather than a Sliver: it is the anchor a tribal deck builds around, not another body in the chain. It also answers the Sliver deck's oldest problem, that a board of small linked creatures dies to a sweeper and rebuilds slowly. This one refills on its own clock and makes the rebuild hit twice as hard.