Entirely Normal Armchair is a uncommon Artifact card from Unstable (UST), collector number 146. Current market price: $0.22 (foil $1.63), TCGplayer market prices via Scryfall.
During your turn, if this card is in your hand, you may hide it on the battlefield. {0}: Return this artifact to its owner's hand. Only your opponents may activate this ability and only if they see this artifact. {2}, Sacrifice this artifact: Destroy target attacking creature.