Unown [U]

Their shapes look like hieroglyphs on ancient tablets. It is said that the two are somehow related.

Pokemon Power — Undo: Once during your turn (before you attack), if you have Unown U, Unown N, Unown D, and Unown O on your Bench, you may return your Active Pokémon and all cards attached to it to your hand.

Hidden Power (10)