Melgar's Fire is a powerful spell that allows the user to summon a rain of burning meteorites over a large area.
The spell was used by Sabrina Glevissig during the war for the Lormark, in order to weaken both the Aedirnian and Kaedweni Army. If not for Sabrina's intervention, King Henselt and his commander Vandergrift would've taken Upper Aedirn which, according to the Lodge of Sorceresses, would've caused an upset of power in the Northern Kingdoms.
The damages of the spell were however devastating: Vandergrift was killed, along with 3,000 soldiers from both armies, forcing Aedirn and Kaedwen to retreat. For this reason, King Henselt punished Sabrina with death.