Callous Oppressor is a rare Creature — Octopus card from Onslaught (ONS), collector number 72. Current market price: $1.66 (foil $12.44), TCGplayer market prices via Scryfall.
You may choose not to untap this creature during your untap step. As this creature enters, an opponent chooses a creature type. {T}: Gain control of target creature that isn't of the chosen type for as long as this creature remains tapped.