Nitor is a base item for Thaumcraft 4, and is one of the first researchable items. It is created in the Crucible. An easy way to provide the essentia is to add 3 coal or charcoal, and 6 torches, for each 2 pieces of glowstone dust to be transformed.
You can place it anywhere as a light source block. The light produced by Nitor is light level 15, the same strength as Jack-o-Lanterns or Glowstone Blocks. It can also be used as a safe heat source below the Crucible itself.
This flame seems to be fueled by magic itself. The number of uses for an everburning flame seems endless, but unfortunately it doesn't seem to produce much heat, though it could prove to be a steady source of light and energy. Nitor can also be placed in the world to act as a magical light source.