Ethereal

Ethereal is a card keyword that means if the card is still in your hand at the end of the turn (unplayed), it is automatically Exhausted. Ethereal cards must either be played during the turn they are drawn or they will be removed from your deck for the rest of combat. This creates a use-it-or-lose-it pressure when Ethereal cards appear in hand.

Ethereal appears primarily on powerful cards with significant effects — the high risk of losing the card is offset by its strong impact when played. Apparition (from Council of Ghosts) is Ethereal and Exhaust, but grants Intangible for one turn. In The Watcher's kit, several key cards are Ethereal. Cards that have Retain or mechanics that interact with card exhaustion can offset the downside of Ethereal. The Exhaust synergies of The Ironclad mean Ethereal cards there trigger beneficial effects even when not played.