Midnight Fire is a Kethic discipline that braids two of the nine elements, fire and dark, into a single working. The result is heat without light. A practitioner draws fire up through the leylines the way any firemage would, then folds the dark element across it, so the flame throws no glow and casts no shadow of its own. The victim feels the burn before seeing anything, if they see anything at all. The school's own name for this is "pain from the shadows."
Outsiders sometimes take Midnight Fire for soul-work or some traffic with the lower planes, and they are wrong on both counts. Nothing in it severs a soul-thread or reaches into the Nethereal. It is fire and dark, two elements, both routed through leylines, both replenishing in the caster as ordinary Kethic does. What unsettles people is the silence of it, not its source.
There is no academy. Midnight Fire passes from one master to a student or two at a time, taught to Kethic casters who already hold a firm fire attunement and have some reason to want their work unseen. It surfaces among mercenary companies, in siege sabotage where a fire that gives no light is worth more than one that does, and in the trade of people who set fires for hire. Most courts that employ a firemage corps refuse to teach it on the record, which has never stopped a few of their members from learning it anyway.