I was discussing the mythology Joss Whedon set for BtVS and Angel.
-Giles to Scoobies, BtVS "The Harvest, Part 2"
And in Angel episode 103 "A Hole in the World" we get to see one of the Old Ones, Illyria, and learn about things like the Deeper Well.
My question is, how can we design Old Ones, demons, and vampires to fit this cosmology? Are demons weak Old Ones, or servitors thereof? The Toruk-Han from BtVS S7 are apparently either the proto-vampiric demons or the first iteration of mixed demon-human vampires (but in the latter case, why are they too locked away beyond the Hellmouth?), so it could go either way. If the Toruk-Han are the first generation of the hybrid form, all's well since the wouldn't need the pure elemental power of the Old Ones. If they are the original demons, they are so weak compared to Illyria they must surely be servitors, as are the myriad other demonic species on the Whedonverse.
Also, judging from the sarcophogai in the Deeper Well, the Old Ones are humanoid creatures to begin with. How would they match up to a creature such as Glory (when she was a true Hellgoddess, at least)? Are the Old Ones and Hellgods of the same lineage, or at least at parity when it comes to power?