I'm pretty far into DC, close to the ending I think. But the transition from an NPC-rich environment, with lots of clues, to a huge deserted area where you are more or less entirely on your own was a bit jarring for me. It feels like another game in a way. I took a brief glance at the quest list for DC and there seems to be quite a few of them that I never discovered, such as capturing a latcher, but I hope they will present themselves in another playthrough.
Anyway, I'm friendly with both factions, and other than the old man, the only real quest I've been given was to rescue the Tchortist prisoners. I can't find a way to do that as my character has no stealth, other than to become hostile with the Faceless. I don't have any speech skills either, not that the Faceless seem to do much conversing with me. A concise lot, them. I generally avoid spoilers but I'll take one on this particular quest, in hopes that it will open up some new options, such as perhaps discovering what's behind that mysterious door in the Tchortist complex with the symbolic terminal.
Oh, and apparently there is just one chance to get the quest to clear the burrowers for the old guy? I saw it pop up in dialogue once, and chose another option, and can't seem to come back to it.
