Observatory is a Mage Trap Room introduced in Boss Monster: The Next Level. It is noted as being a "cycling" room, meaning a player can discard a card to activate its effect.
Strategy[]
A card simply meant for a player to obtain a new Spell card if they have on in their hand that seems lackluster.
However, this also works by gaining more Spell cards in general, as this card also potentially pairs well with Cleric cards that allow a player to take Spell cards from the discard pile.