Abstruse Appropriation

Theft with a mana-fixing clause built in, which is what separates this from the long line of "steal target permanent" instants that came before it. Most exile-and-recast effects hand you a card you cannot pay for: rip a five-color bomb off an opponent's board and you are left holding a permanent your manabase never intended to cast. The devoid shell and the colorless-mana permission answer that problem sideways. The card does not let you wash any mana into any color; it lets you spend colorless mana as though it were any color, so a source of colorless mana (a Sol Ring, an untapped Wastes, a diamond) becomes the currency that pays for the stolen spell's colored pips. That reframes the effect from a tempo swing into a genuine acquisition: you are not borrowing the permanent for a turn, you are annexing it into your deck's economy, provided you can feed it colorless. The instant speed is the other half of the design. Because the exiled card stays castable for as long as it sits in exile, holding this up at turns it into a reactive answer that converts into a permanent resource: point it at a fresh planeswalker, a mana rock, or an attacking threat, and the removal doubles as ramp or a body of your own. The ability cares nothing about the exiled permanent's colors, and colorless mana is merely an option, not a requirement, for casting it.