Essentially they are extremely advanced and what can be described as a synthetic semi-robotic and act as observers. Their tech is fascinating, however one is similar to a mind palace or prison, and it can go through everything you know. Which is brilliant when you're trying to figure out a solution to a major problem.
However, it again will literally create whatever you think of. So you feel seven? You're seven and creating a precursor to TNT. Or you suddenly remember being thrown to the bottom of an ocean? Ocean water breaks the windows.
Or you get a physical manifestation of something that is only supposed to be representative.
Actually both since the mind prison device is also here.