Radiant Lotus is a mythic Artifact card from Aetherdrift Promos (PDFT), collector number 240p. Current market price: $1.02 (foil $1.32), TCGplayer market prices via Scryfall.
{T}, Sacrifice one or more artifacts: Choose a color. Target player adds three mana of the chosen color for each artifact sacrificed this way. (Activate only as an instant.)