Archelos, Lagoon Mystic

The trick is that the toggle points both directions from a single body, and both halves of the text are live. Most "permanents enter tapped" effects are pure disruption: a static that grinds an opponent's tempo and yours alike, symmetrical and unsteerable. This 2/4 lets you choose which side of the effect you live on by managing one turtle's tap state. Tap it (in combat, to an activated ability, to a convoke or crew cost) and every permanent your opponents deploy stumbles onto the battlefield tapped, arriving a full turn behind on blocks and mana. Leave it untapped and the other clause takes over: "permanents enter untapped" overrides the tapland text and comes-into-play-tapped effects your own manabase is riddled with, so a board that would normally arrive stalled instead arrives ready. That untapped mode is genuine upside, not a dead clause. What lifts it above a prison piece is control: because you decide when the turtle taps, you decide which half of the text is active during a given turn cycle, closer in spirit to a Winter Orb you can switch off than to a hard lock. Worth noting what it is not: the effect applies only as permanents enter, so it never taps or untaps anything already on the battlefield. A shaman turtle in Sultai colors was never going to headline a set, but "one creature decides how everyone enters" is a cleaner take on tap-state matters than the fixed statics before it.