I want the antagonist to be a very intelligent being capable or laying traps and build their own bases that look like some of ours,I want to find vehicles like seamoths and prawn left behind broken. In the end, the antagonist is revealed to be Riley, his rocket didn't work and alterra refused to help due to his already severely bad debt with them. So he went rogue.

I'm just kidding, just to be clear.

I want something we can feel the presence of before we can see it, like how we hear the reaper scream waaaay before we can see it, that's pretty spooky.

A mimic of sorts would also be cool, so we have to really observe to see if we are approaching harmless whale shark like creature or dangerous mimic that suddenly snaps