Elicon is a Boss card and a Kickstarter Exclusive Promo Card.
Rulings[]
This only doubles treasure from your Rooms, not this Boss card or other effects.
You cannot choose whether to use this ability when you Level Up, nor can you specify which Rooms are affected. All Rooms in your ability double their treasure value
Strategy[]
Elicon's Level Up Ability is used best in a situation when the player is mimicking their opponent's treasure values as best as they can, thus causing a build up of Heroes in town. Upon activation, all Rooms in the dungeon have their Treasure Value doubled, which would then lure in every Hero in town. This is a risky move, however, as it can mean either the player's victory, or their doom. Especially if Item Cards are being used.
Elicon's Ability is also good to use when in a Treasure stalemate with an opponent over one particular Treasure, and can assure the player can break the stalemate.