azoth in its pure, gaseous form. In this form, it suffuses the space between the worlds and stars, transmitting both energy and light. Sages say that quintessence is the most sublime of all the elements, being the very stuff of magic from which the gods wrought the cosmos.
Though a gas, quintessence behaves like a liquid, which is why old texts speak of "sailing the Quintessential Sea." With the right sort of vessel and the means to launch it into the Astral Plane, it is indeed possible to sail through quintessence to other worlds and, theoretically, even the stars themselves. Of course, no one has done this well before the fall of the Thulian Empire, but the knowledge still exists; all that is lacking is the will to pursue it.
Long ago, for reasons none can explain, quintessence rained down on some worlds and satellites, becoming liquid azoth. Areon once had the largest deposits of azoth of all known worlds, but they were squandered by the Eld, who used it up in their quest for cosmic domination. It was, at least in part, the lust for more azoth that led the Red Elves to conquer other worlds, a lust that survived even the loss of their empire. Even now, they covet other worlds' azoth and dream of the day when they might claim it for themselves. Meanwhile, magicians and alchemists alike seek out azoth for their own purposes, knowing well that even a minute amount of it can be used to work wonders.