Green crystal- spoiler

I never saw it actually get used, but it was in front of the xeno mural, so maybe it somehow links up... dunno....

I don't think anybody knows. Maybe it was something like the original alien DNA sample that the engineers had stored? Kind of like the dragon fly trapped in amber like in Jurassic Park film? Or perhaps it was a lump of engineer poo?

@facebugger...interesting that it may have original Xeno dna in it. Good thought...

Noooooo.......its obvious init? Superman kept bugging them until they found some Kryptonite lol

Perhaps it powers the hologram stuff? Same colour init? Or it could be to power the entire ship......usually crystals arnt they.....dilithium and all that.

Following my original thought, maybe the xeno's are an older species than the engineers. Maybe the engineers evolved form them in someway? Maybe they found some preserved DNA and were trying to recreate them and created humans as a host for them because they wanted to bring back a long lost race? Might explain the mural in the room if they regarded the xeno's as a higher race or something. Just a thought.

That makes sense, seeing as there's a tomb right below it as well. Maybe it wasn't just another tomb... I was hoping they would've explored it more, but maybe a later movie???

unobtanium

The ghosts were all running into this room. As far as I know the room contains urns, a giant space face, and the xeno shrine with the green crystal. So I think the crystal does something connected to xenos, that could save the ghosts: maybe its Ctrl+Alt+Del for the black goo.