To return to the specifics of the Temple of the Eye, which we find in areas 9-11 of the second level of the Hall of the Fire Giant King, we find here a fully functioning shrine to the Elder Elemental God, one of the images is quite striking, even given the Lovecraftian theme of the area:...a scene of various creatures crawling, then creeping, up to huge, vaguely squid-like creatures with 10 hairy tentacles. In the forefront of this mass self-sacrifice are elves and men, but ehre are also dwarves, gnolls, orcs, trolls, halflings, ogres, goblins, etc. amongst the crowd. Those near the monsters are being torn apart and eaten as dainty morsels. There are 3 of these ghastly things, mottled in various shades and tints of purple and violet.Three??? What might that portent? It's quite obviously something that hearkens back to the stories of Lovecraft, but why would there be three squid-like things, in a temple supposedly to the "Elder Elemental God" (note the singular)? Obvously it's not the EGG itself being depicted. Perhaps... just perhaps... they are priests or elder worshippers of the EEG, rather than a representation of the EEG itself. More HPL goodness (and maybe those things are still to be found in the Depths? Serving House Eilservs as advisors? Oh wouldn't THAT be interesting to show to a rival house in Erelhei-Cinlu)
There's lots of good stuff here, and if you plan on running those adventures, the Elder Elemental God easily lends itself to be a central theme of the series, a mystery to be puzzled out by the PCs as they work their way towards the center of the conspiracy. Even if you don't, there's lots of inspiration here for your homebrew adventures and campaigns.