Urza's Tome

Every activation is a break-even loot on its face: draw a card, then throw one back. What turns that filtering into an attrition engine is the escape hatch in the "unless" clause, which lets you exile a historic card from your graveyard instead of discarding. Feed it that fuel and the base action becomes card advantage, one net card per turn across a long grind; run dry and it degrades into pure smoothing, cycling through your deck without adding to your hand. The dependency is what keeps the cheap, repeatable rate fair: the mana is trivial and the activation never expires, but the card economy is borrowed from a resource the deck has to manufacture elsewhere, by burying enough artifacts, legends, and Sagas that you can afford to spend them. That's the tell for the kind of shell it belongs in. It doesn't ask for a single build-around; it asks a deck to overcommit to a card type and then quietly launders that commitment into raw cards over the course of a game. The historic theme was built to glue those overlapping type-matters payoffs together, and this rewards precisely the decks that lean into it, converting graveyard density into throughput at a rate you set by how much material you're willing to spend.