Part two requires me to finish writing up the various statuses of the extant editions, and I've just been lazy about it lately. I hope to finish it by year-end.
The Lost Gods are a group of beings unrelated to Tharizdun---they're primeval figures, and form a cycle of background myths and legends for the gods themselves. I've used some of the details from the DMG1's artifacts and relics as part of their heritage (the Throne of the Gods in particular).
You'll see more as I compile more old notes, manuscripts, etc.