Elementalist's Palette is a rare Artifact card from Commander 2021 (C21), collector number 76. Current market price: $1.49, TCGplayer market prices via Scryfall.
Whenever you cast a spell with {X} in its mana cost, put two charge counters on this artifact. {T}: Add one mana of any color. {T}: Add {C} for each charge counter on this artifact. Spend this mana only on costs that contain {X}.