“Do you know he has an entire room dedicated to himself, complete with a life-size statue made of Lumenite? It glows, guys. I’m going to have nightmares about it.”
Lumenite is a material that was used for building Lumenaria (which is the origin of its name) when the Ancient Councillors built it. It does not burn, even with Everblaze, so it is also used for bottling said substance when necessary. It is a mineral that glows with a white glow.
However, in Lodestar, the Neverseen find a way around the no-burn rule and the confusing hallways and staircases, using Gethen to collapse the Lumenaria castle using outward channelling (a skill) during the Peace Summit, killing Mr. Forkle's twin (as revealed in Nightfall) and Brant while Councillor Terik lost his leg.
Fintan Pyren was once held in a Lumenite prison for a short period of time due to its resistance to flame.