Formless Darkness liquid like what that one guardian was hauling on the sparrow (sparrow you get from yeeting Rhulk on master) that when near a living being it will creep up on you to enter you (he blew himself up by use of his sparrows nuclear core, so he could be reformed by his ghost before he himself would lose control of his body after it tried getting in him (Reason why all that happened is because he crashed his sparrow that was carrying those vases containing that stuff that's supposed to be tightly sealed by the guardians bringing them back from the Pyramid on their expeditions inside to find stuff and the goo got loose so...) My guess is Nezarec is either: Darkness mustered up enough intellect through time and effort after the Darkness was created (if Savathun is to be believed when she says the Darkness was created by a higher being, both as a power but that also has a will of it's own) into a first being although still formless, thus still requiring a body, making Nezarec the first of his kind Or, eh he's just like the wormgods or Ahamkara and can transcend death meaning body or not doesn't matter to it, since it can just possess any corpse it wants (key word, corpse, not living being, Osiris was basically given back to us "dead" in a way... So how convenient that the one only thing that can bring him back is some Pyramid original pure black roast Nezcafe lol? Nezarec even said it best in the fusion we got this season, we think him frail, contained, made easy to use [the relics including Delicate Tomb exotic itself being one, flavor text says so, including exotic perk name], but he isn't, he is just "diffused" as he said in his own words.. all he was waiting for is for someone to gather him up and do it) My guess is that this will be a downside for Osiris, he is given something, but in return something will be taken, logically.. real question is what? If Nezarec's curse is to be believed then most likely Osiris will have to deal with the remainder of his lifeforce get sapped away by Nezzyboy in him slowly vacuuming him dry until he's just a husk for Nezarec to control then reform into a new shape after regaining his strength from consuming lifeforce