Runed Terror is a rare Artifact Creature — Elemental Champion card from Mystery Booster 2 (MB2), collector number 610. Current market price: $0.17, TCGplayer market prices via Scryfall.
Instead of taking turns as normal, players take their phases sequentially. (For example, you take your beginning phase as the active player, then the next player in turn order becomes the active player and takes their beginning phase. After each player had a beginning phase, do the same for first main, combat phase, second main, ending phase, and then beginning phase again. If this creature leaves the battlefield, the active player continues their turn as normal.)