So I realized that a plague in my universe that effects not only people but their environment does a similar thing to what the Xenomorphs do for their nests. It spreads and causes the environment to become covered in black ooze that can effect anyone who steps on it but I don't know how the best way to describe it is. So how would you best describe this image?
I'd describe the xenomorph goo (or the creep from Starcraft, it's similar) as a sticky, wet web of tough green/gray biological strands. Words like that.
It was a dark murk across the land, spreading like a fungal growth composed of crude oil. It would not burn. It could not be scraped away. We dare not touch it.
A sour, chemical vapour hit them as they emerged into the (hub?) I felt my foot slide and looked down to see black oil pooling across the floor, with some suction resistance I lifted my foot. 'It's oozing out of the walls' said - from over my shoulder. I looked closer and saw with horror that it was, thick dangerous oil oozing out of the ? and the ? like the sap of a living tree. We quickly retreated back along the narrow passage way we had came.
"The room was poorly lit, it's walls a cold grey tone and on them, a black ooze seemed to form organic shapes, as if the whole place was the inside of some larger, uintelligable deceased creature. It seemed to almost crawl upon every surface, as if it had a mind of its own, ready to consume anything that would come close"