Oasis Ritualist is a common Creature — Snake Druid card from Hour of Devastation (HOU), collector number 124. Current market price: $0.14 (foil $0.24), TCGplayer market prices via Scryfall.
{T}: Add one mana of any color. {T}, Exert this creature: Add two mana of any one color. (An exerted creature won't untap during your next untap step.)