Ooh, Psychomatons are interesting.
Though really that depends on what take you're going for on them. I've seen some writers posit that they were essentially micro-God Constructs, tiny slivers of the Eldar Racial Gods that were used for literally everything in the Eldar society (The things that basically guranteed they were a post-scarcity despite the fact that literally every man and their dog was engaged in murder-orgies on an unfathomable level). This kinda explains why they shut down and became more dangerous to the Eldar after the Fall than anything else, what with being directly inhabited by aspects of Slaanesh.
Others see them as just being wraithbone constructs but pushed to the maximum limit. Essentially Wraith Shoggoths that were the Eldar equivalent to the Men of Iron.
Edit: Seeing that the actual ship, which might actually be a proper Eldar Warship judging by what its purpose was, was so close to Terra itself, that's super interesting. Was it intended to just act as a 'we're bored of this race now, eliminate them'? Or something closer to just facilitating Wyld Hunts?