As long as a player has an adequate way to keep mutating upon an Archipelagore, some creatures will never be able to untap normally
playing temples, gates, and gain lands over fetches, shock, and duals is a great start, but what about all the fancy lands
Unbound Flourishing - If you're running a +1/+1 / spell hybrid build, this card makes everything explode in value
You can supplement powerful instants and sorceries to up the potential of this card, but more often than not, even the opponents cards will be enough to make Mysterious Stranger worth it
Time Walk is one of the strongest cards of the Power Nine, as it gives the player an entire extra turn for the measly cost of two mana