Magosi, the Waterveil

Time Walk as a land, sold to you on layaway. Extra-turn effects have always lived in the discomfort zone of design: powerful enough to chain into a loss for your opponent, dangerous enough that Wizards almost always taxes them heavily. This one charges the tax up front, in turns rather than mana. You spend a turn doing nothing but loading an eon counter onto the land (skipping your next turn entirely), and only later do you cash that counter back for the extra turn, bouncing the land to your hand in the process. The net is roughly even on tempo: you lose a turn now to take one back later. What you are really buying is the right to schedule that extra turn, to spend it on the turn that matters rather than the turn it ripens. The bounce clause is the quiet engine here, because a land that returns to hand can be replayed and reloaded, which is what turns a fair-looking Time Walk impression into something with an actual ceiling. Most extra-turn cards are one-shot spells that exile or sit dead in hand; this one is a permanent that keeps its counter banked across the board, immune to most ways of answering a spell, and patient enough to wait for the turn its controller has been building toward.