I tried looking up what are the various gods worshiped by the inhabitants of Terrinoth, but I had no luck. The only ones I was able to find are Kellos (who seems to be the most commonly worshiped deity), Kelnov (the banished All-Father), and the Primal Gods of Zanaga (who I don't think are worshiped on Terrinoth).

Anyone a little more familiar with the lore know a bit more about the religions?

Those are the big ones. Kellos's followers form the central religion espoused by the Free Cities and the Daqan Lords , so his faith pretty much dominates in Terrinoth proper. All the heroic warriors we see decked out in red and gold are the Knights of Kellos, btw. A holy order of warriors, although not paladins in the traditional sense (to my knowledge none of the lore has explicitly declared that Knights have any magical powers granted by joining the order. A few individual characters may have magical powers in addition to being Knights, though.)

Other faiths mentioned, mostly in passing, include Kyros (a diety worshipped by giant-kind,) the Serpent Gods (a trinity of deities worshipped primarily by serpentspawn (snakemen,) and Fortuna (a god of mysterious origin who appears to have dominion over fate.) She appeared in a couple of quests in 1E as a giant gold dragon with pupilless eyes.

In the Torue Albes they worship a pantheon called the Seven Brothers. We don't know anything other than the name. I like to think that Kellos, Kyros and Kelnov are 3 of the 7 brothers, but there's nothing to support that theory.

Android is getting a book about the setting, I hope someday they give terrinoth the same treatment.

I've thought about building a campaign using the online tools but must admit that the thing stopping me is my lack of knowledge in Terrinoth lore. It such a shame that there's a real lack of online material about the universe. If you think about what was created by FASA for the Battletech universe or Games Workshop for the Warhammer games, FFG is missing a trick.

I think if they releases an online scenario builder for Imperial Assault they'd be a bigger uptake; simply because the universe has tonnes of material to draw from. Let's hope we get some novels or an online compendium.