Awakener Druid

The whole investment rides on a single 1/1. The body that enters is fragile, but the four-power threat it makes is fragiler still: the conditional clause ("for as long as this creature remains on the battlefield") means the moment the Druid dies, the 4/5 reverts mid-combat to a Forest that taps for mana and nothing else. Kill the Human, and the Treefolk vanishes with it. That dependency is what pays for a four-power body attached to a three-mana spell, and it cuts in both directions: a removal spell pointed at the 1/1 unwinds the entire package, while a bounce or blink lets you re-target a fresh Forest and rebuild the threat from scratch. Timing favors the attacker more than it looks. Because summoning sickness tracks how long you have controlled the permanent rather than how long it has been a creature, a Forest you played on an earlier turn can swing the moment it is animated; only a Forest played the same turn sits out a combat. The quiet liability is the land staying a land. Your animated Forest now answers to creature removal, gets swept by board wipes, can be edicted away, all while you still need it for mana. This is land-as-creature design at its most exposed, a narrower descendant of the sweeping enchantments that turned every land into a creature: precise where those were total, pointed where those were a blanket, and brittle in a way neither was.