My bad, I confused it with Liliruca's location in her quest. In that case, it should be on floor 9, the entrance to floor 10. Same location as the rest point (campfire icon) on Floor 9.
Just for clarification, is it exactly on the campfire icon? Or somewhere near? Cause I can't see a quest marker at all, and it still says reach floor 9 for the Nemisis quest line.
