Aetherling

The blink ability solves the whole engineering problem at once. Exiling itself and returning at the next end step does two jobs on one button: it dodges every sorcery-speed answer, and it sidesteps any wrath or targeted removal that would resolve while the creature is gone. As long as there is blue mana untapped, this is a finisher that simply cannot be killed: it leaves before damage can be dealt to it and before removal can find it. That is the design reading clearly: a deliberate answer to the perennial problem of the control deck's win condition dying to the same removal the control deck spent the whole game baiting out of the opponent. The two stat-shifting abilities handle combat math, trading toughness for power to push lethal or shoring toughness up to survive a block, and the unblockable line guarantees the swing connects. Every ability costs mana, which is the discipline holding the package together: a single Aetherling is a slow clock, and making it evasive and protected in the same turn drains real resources. But a control deck that has stabilized has nothing better to spend mana on, and the more mana it accumulates, the more inevitable the Shapeshifter becomes. The danger is overspending into the pump abilities: drop the toughness modifier to zero and state-based actions kill it on the spot, before any flicker can save it.