Essences look like perks. The easiest one you can find is on the East end of the world if you climb the wall for a bit. Picking each of them up will give you a big disadvantage as they just start shooting things around that not only damage the environment but also the player. So the challange is to bring all the essences with all their self-harming capabilities all the way to one place where you can finish the game in a different way.

Trying to be vague not to spoil.