Internal fire

Internal fire was a powerful spell commonly used by wu jen in Kara-Tur. The spell was very rare outside Kara-Tur, although some fire mages in Faerûn knew of the spell.

Effects
When cast, this spell created a fatally intense amount of heat inside a target. The target eventually burst into flame, killing them instantly. If the target had an item or equipment that gave fire resistance, they were unaffected by the spell. A creature with a natural immunity to fire would also be unaffected by this spell. If a wu jen cast this spell in the phlogiston, the target, instead of bursting into flames, exploded. Any creature within 5 feet (1.5 meters) of the target suffered damage as a result.

Components
In addition to verbal and somatic components, the spell required a material component, an iron canister filled with hot charcoal.