During your turn, if Entirely Normal Armchair is in your hand, you may hide it on the battlefield.
: Return Entirely Normal Armchair to its owner's hand. Only any opponent may activate this ability and only if they see Entirely Normal Armchair.
, Sacrifice Entirely Normal Armchair: Destroy target attacking creature.
Your opponent may activate Entirely Normal Armchairâ€™s first activated ability even if they canâ€™t literally see it, provided they can identify where it is. That is, you canâ€™t just put your hand over it and claim that canâ€™t see. Well, you can claim that, and it might be true, but it wonâ€™t do what you want it to.
You must legally get Entirely Normal Armchair into your hand before you can attempt to sneak it onto the battlefield. For example, you canâ€™t sneak it in from your sideboard or collection during a game.
Entirely Normal Armchair can be hidden in plain sight (i.e. just sitting there).