Deeproot Historian
Retrace was a fringe mechanic when it first appeared: a way to buy back an instant or sorcery from the graveyard by paying its cost plus discarding a land, which demanded floods of excess lands to keep humming, and precious few cards ever carried the keyword. Grafting that ability onto a creature type is the wrinkle here. Instead of casting the same spell over and over, this hands retrace to every Merfolk and Druid sitting in your graveyard, converting a tribal creature pile into a recastable resource as long as your hand keeps supplying lands to pitch. The land-discard cost throttles the engine into something other than free card advantage: each recursion trades a card in hand for a body on the battlefield, so the loop runs only as fast as your surplus lands allow, which quietly favors a deck built to flood. The body is incidental. What matters is that it turns a graveyard full of dead Merfolk and mana dorks into a slow, grinding stream of creatures, a recursion axis green and blue tribal decks rarely get access to. It is a narrow key that fits exactly two locks, but for decks stacked with those creature types it reframes the graveyard from a dumping ground into a second hand you refill one land at a time.
