Thunderkin Awakener

The toughness clause is where this design gets clever. Most reanimation gates on mana value or a keyword; here the restriction is a comparison against the returned creature's own toughness, so a 1/2 body can only pull back Elementals with a single point of toughness. That comparison is dynamic rather than fixed: grow the Shaman with an anthem or a counter and the pool of legal targets widens with it. The catch is timing. The attack trigger needs a target, so the target has to be legal when the ability goes on the stack, which is the Declare Attackers step. You cannot see blockers first, and you cannot pump mid-combat to reach a bigger target: the body has to already be large enough before you declare it as an attacker, or the fatter Elementals in the yard are simply not choosable. Haste means it comes down and starts feeding itself the same turn, and because the returned card arrives tapped and attacking, you skip the summoning-sickness tax entirely: it swings this turn, then dies at end step. That sacrifice is the price, and it reframes the whole engine. You are not rebuilding a board; you are renting a body for one combat, which points the deck toward Elementals that want to die repeatedly (a strong death trigger, or a creature whose only job is to connect once). Narrow recursion by construction, with a ceiling set entirely by how big you can make the little Shaman before combat begins.