The Mind Stone

A mana rock that walls off its interesting half behind a paywall, and the design's entire balance lives in the size of that wall. Tap it for white the turn it lands and it is a plain two-drop utility piece; the payload waits behind a separate six-mana harness activation, paid whenever you can afford it, as a deliberate speed bump. That gating carries everything: once harnessed, you get a recurring, no-mana end-step blink, and a free blink every turn is the kind of engine that would be oppressive if it came online off a two-drop for free. Splitting it into two stages turns a would-be turn-two problem into a mid-game commitment. The blink itself is quietly precise: it exiles up to one other target nonland permanent you control and returns it under its owner's control, so it rebuilds enters-the-battlefield value, resets counters, and untaps whatever you point it at, while the "other" and "nonland" clauses keep it from looping the Stone itself or your lands. Crucially, it fires at the beginning of your end step rather than at instant speed, which makes it a value engine and not a defensive tool: the trigger uses the stack and both players get priority, so an opponent can respond (killing the target before exile, for instance) rather than watching the blink function as an escape hatch. Indestructibility keeps the harnessed engine off the board wipes that would otherwise demand a second six-mana investment. It is a rock first and a value loop second, and it earns its ceiling by charging for that ceiling up front rather than folding it into the rate.