Hydroform

Animating a land is an old idea built on a permanent commitment: enchantments like Living Lands turn your mana base into a standing army and then ask you to ride out the risk that one removal spell now costs you a land and a turn of tempo. Doing it for two mana at instant speed flips that math. The land is only a creature on your terms, for the swing in question, and reverts before an opponent's untap step can punish the trade. The flying clause is what earns the slot. A 3/3 ground body off a land is a marginal upgrade over a creature you already control; a 3/3 flier is an evasive threat conjured from a permanent that was nothing of the sort a moment earlier, sailing over blocks your real creatures cannot. That makes it a hidden finisher rather than a board investment: the deck develops lands as lands, then turns one into a surprise attacker or a flash blocker, asking nothing of your board until the moment you decide to cash it in. The tempo bites at both ends. You have to pay the two before the land swings, so if that mana comes from the land itself, it is animated already tapped and cannot attack. And once a land does attack, it taps, leaving you short a mana source until your next untap step. The trick wants extra mana to fuel it cleanly, not a bare untapped pair.