Not Thargoids. Something you can see, in the original Elite (and for that matter the sequels) without even leaving the station ... though it's perhaps more of a risk if you do leave the station!
I don't know why you are all so nervous to answer the clue. If you don't like setting the next clue you should just do what I do.. make up a simple one. The clue's answered quickly and the poison chalice passes to the next person