Chronobot is a rare Artifact Creature — Construct card from Mystery Booster Playtest Cards 2021 (CMB2), collector number 105. Current market price: $0.16, TCGplayer market prices via Scryfall.
When Chronobot enters, switch upkeep steps with target opponent for as long as it remains on the battlefield. (You take your upkeep on their turn, and they take their upkeep on your turn.)