NPC I-more aimed at interacting with the deity-worshipping folks of the DoD
My first thought would be an immortal, akin to Ioun-however, due to magic failing, they couldn't really have been mortal in the first place. I was thinking of an outsider who's spent a longgg time on Spira, perhaps a fallen angel if you want to make roleplaying interactions more interesting (Something once good but now neutral, opposed to a devils/demons, which the party may have already faced during Agar's wedding phase

). If you plan to go that route, might I suggest a figure with a personality akin to Dorian Gray (a handsome man turned immortal who has been corrupted from innocence into debauchery from the story
The Picture of Dorian Gray, although he's also depicted in
the League of Extraordinary Gentlemen)? In DnD terms, he could be have class levels in the Sensate PrC in one of Dragon's Planescape features, which would make 'sense' (pardon moi for the horrible pun) as sensates value gleaning information of all types. As for the specific outsider used as a base, either a Fallen Trumpet Archon (being a former herald would relate even more to the knowledge/info. theme) or an Eladrin (perhaps more sense as a chaotic outsider). If this idea interests you, I'd be happy to stat something up.
NPC II-poor, poor Agar
Well, you're dealing with Worms right? Who would know better than a Vermin Lord, ala BoVD? Maybe with some levels in Cancer Mage, depending on how powerful he is. Maybe he's a former student or even colleague of Hagiok? That brings to mind, will/have the DoD spoke to Hagiok? Maybe Teliez has cured him of his insanity? Anyways, back to the Vermin Lord, perhaps throw on an undead template such as lich to give him more credibility. But above all, make sure he has tons of insects/vermin creeping around and about him (or through him if he's a lich). Maybe a Son of Kyuss cohort, if you feel particularly sadistic towards the poor alienist. Again, I'd be happy to stat this charming fellow up if the idea interests you.
Edit-On the more "goody two shoes" side, a Loremaster would be pretty standard. I'll try and come up with a neat twist on this though, and get back to you.