I went down Abyssal Station Zero, retrieved the Acorn and ran away from black indestructible clouds coming out of the monolith. I obtained a feat which increased range of psi powers after inspecting said monolith.
I went back to camp, didn't give the Acorn to the Professor and kept the Acorn on me for the time being. From speaking to Aran, it's an object which can has power aid in creating other powerful objects (or something to that effect, he wasn't super helpful).
My question is - what was that monolith? It was slightly broken. From reading the information scattered around the facility, the Lemurians had found it somewhere and brought it to the facility. It must have affected the minds of the engineers, although the last piece of info I read was that they brought a flat grey disk to cut a piece off the monolith (which I assume they succeeded in, given that it is slightly broken). I know nothing else however.
Thanks!