I figured it was Killy. After Cibo turns into the level 9 and Killy spends over 14 years putting himself back together we get a lot of short flashbacks, one of which is of Dhomo (still with two eyes) and Iko (who is waving and still has a body).

In order to remember them Killy must have seen them before, right? In Balme! and so on Nihei mentions that Killy's been wandering around for over 3000 years, but that brains only have 30~50 years worth of memory space. Dhomo lost his eye around 250 years before Killy and Cibo meet them (the 2-million-and-odd hours ago flashback) and by that point Iko had already became a floating head, so Killy must have met them some time before this.

Given the detail Nihei usually puts into his work and the way he leaves it for the reader to figure stuff out I don't think he'd mention soemthing happening once before and not have it relevant in some way.

Well, isn't Killy the only one who can wander trough the megastructe levels, because he has a GBE. So he is technically the only one able to use this elevator, because all other people can't switch between the levels.
Combined with the post before, it seems to make sens

Just wondering, but could it at all be the other "Killy" that he sees in the final chapter?

That character also has a variation of GBE as well.

And why not the Silicon Creatures?

If they are in that level this means that they have to get there first, right? Possibly using that elevator. Dhomo and the other Safeguards could teleporst themselves. And if Killy has any memory of Dhomo probably it is from some other place. When I read that volume I had the feeling that Dhomo had a life before that and was activated when needs arise. That level is "new", probably he and Killy did meet each other in other place, in point of the past, probably when both were doing some work for the Governing Agency. And only if they really met.

Actually looking back, that might be more likely possiblity. is the page of Killy remembering Dhomo and Iko but the last panel on has what looks like the two of them standing on a ledge. The buildings look more like the ones at the edge of the city than the one in the unofficial level.

Maybe they met at the edge of the city and then Killy set off down into the lower levels looking for net genes? Or maybe this was way back when the unoffical level was being still built and it was the edge of the city, what with the city constantly expanding and everything? It could even be before they were designated as SG, since NOiSE shows use that humans can be made into special safeguards? That last one might explain why Killy doesn't remember the SC. I agree that Dhomo most likely had some sort of life before being activated (and that prehistoric fish tie into it). As for the new level still being 'new', I thought it was simply old and incomplete? Maybe I'm overthinking this?

Of course, this is assuming that the colour pages at the begining of chapter Chapter 51 are Killy's memories. [/url]