The Mana Rig is a mythic Legendary Artifact card from Dominaria United Commander (DMC), collector number 28. Current market price: $0.76 (foil $0.83), TCGplayer market prices via Scryfall.
Whenever you cast a multicolored spell, create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.") {X}{X}{X}, {T}: Look at the top X cards of your library. Put up to two of them into your hand and the rest on the bottom of your library in a random order.