I found her underneath a big rock along with a bunch of much smaller Lasius niger workers, so I suspect it might be a queen. I know Lasius niger doesn't have soldiers, so what could it have been doing there if it wasn't their queen? Also, sorry for the bad picture quality, I couldn't find a better camera, and also don't have a proper magnifying glass.
Location: underneath big rock
Behaviour: calm when walking in lighted up areas
Species it was found with: Lasius niger workers running around frantically (note: this specimen was much bigger than the workers)