A couple of things to consider:
1: Tharizdûn is currently imprisoned somewhere, so an Aspect should be made and given stats.
2, and the important thing: Tharizdûn is not only a deity, he's also an Elder Evil.
As such, not only is he in need of Epic Feats, he and his Aspect also needs a couple...
Something to keep in mind: Tharizdûn is also an Elder Evil, so here's a couple of things he has:
Anathemic Secrecy: Tharizdûn is immune to divine divination spells and effects.
He also needs another Elder Evil trait, which would most likely be the one his spawn, Shothragot, has.
Also...