I hope the dev's and writers have watched the anime HunterxHunter. I've read about Essence and have gathered that it is a more vague version of nen. It would be great if the player/character power system of this game was well explained and not open to interpretation.
Safe Link to a youtube video about HunterxHunter's Nen(Essence) explained:
https://www.youtube.com/watch?v=sCk7ebI7Vk4
If the essence is left vague it would be difficult to get into our classes.
Side note: still hoping to get a true swordsman class that isn't using vampire healing.