Exporting the xml file now. Interesting note: there are 1000 unrecorded "Civilizations and Other Entities" reported in a world in which everything is supposed to be already revealed. Those are probably camps and what-have-you... but that's much higher than I've ever seen without the Hell Demons.
UUUUUgh why do map files take so long to export in the current version.
LegendsViewer shows no less than 23 unknown entities, 10 of which must be the standard underground civs (which I modded the max number of), and the other 13 which are the Hell Demons. Problem is, there is no information on them at all. No foundation dates, no sites, nothing.
The Historical Entities, which were set to "do not cull" are equally silent. There are the standard 2 demons which escape from hell and become leaders of certain civs, but not one more. And their names do not match the naming scheme of a civilization with the Goblin language file.
Underground Regions was equally disappointing. The only activities reported in the Underworld were the escaping of the above mentioned standard demons, NOTHING on the Hell Demons. The usual Dwarves, Kobolds, and Drow can be seen adventuring in the darkness of the caverns, but other than that no activity in the Cavern layer, either.
Errorlog.txt is clean, no problems were thrown up in the generation of the world or it's loading into Legends mode.
I am going to go around with a super-powered Adventurer and see if RuneSmith shows anything in the deeps, then maybe try to dig down into hell with dfhack. But I'm not hopeful.