"Unique spell! (Only one copy allowed in each deck.)

Choose a card in your hand.
Remove this card from the game, and put a copy of the chosen card into your hand."

Cost: 4

Domain: 3 Neutral

Wait what do you mean it doubles a card in your hand?

Yes. If you have a dwarven hall in your hand, and you chose the dwarven hall, the copy will become a dwarven hall. You will then have 2 dwarven hall's in your hand instead of just one.

interesting...