Mirrex

The middle line is the tell. Mite-generating lands are usually flat colorless taplands with a mana-sink stapled on: pay three, tap, produce a body over and over. Here that job is intact, but the design adds a one-turn window of any-color fixing that vanishes the moment the land stops being fresh. Play it the turn it comes down and it fixes like a rainbow land; leave it on the battlefield and it reverts to a colorless source until you have three spare mana and the appetite to grind out Mites. That gating rewards holding the land in hand rather than developing it early, an unusual incentive for a piece of fixing, since most manabases want their fixing down as soon as possible. The Mites themselves are the long-game payoff: 1/1 bodies that can't block but carry toxic 1, so the ability turns floods of excess mana into an incremental poison clock. What the card ultimately balances is fixing against inevitability. It is worse than a dual land in the early turns unless you sequence it correctly, and worse than a dedicated threat unless the game goes long, but it asks for neither a color commitment nor a nonland slot to do both jobs from the mana row.