Jewel of Numestra

A large jewel of unknown type, as the color constantly changes, it was once the possession of the powerful sorceress Numestra. Supposedly using Dragon magic, Numestra enchanted the Jewel with the ability to amplify any arcane spell cast into it. It worked and was given to the kingdom of Agria so they might use it as a means to defend the palace from attacks.

It was used by the forces of the Thanarian Deep to amplify a darkness spell, which only made it look like the sun didn't rise in the city. Under the cover of this artificial darkness, their forces attacked the city. Due to the party deactivating the Jewel, the attack was cut short when daylight caused a majority of the forces to flee.

Like most Dragon magic, it often changes the spell slightly and has random side effects, so the Jewel is used only when necessary.