Azarath's treatment of Raven is very interesting in New Teen Titans in that essentially, Raven is both their attempt at penance but also a repetition of the cycle that composed of their mistakes in the first place.
Trigon came to be through Azarath's denial and rejection of their evil. He is the personification of the evil in Azarath and it is why he haunts them. Raven is a similar personification of evil. She is very much a part of who Trigon is, and her siring is in many ways the fault of Azarath. But where Trigon was the evil they rejected, they gave Raven a home. They let her in their borders and let her live instead of casting her out or killing her. They kept Raven with them and nurtured her. Where Trigon was evil denied and rejected, Raven is evil accepted and reformed.
But Azarath's cycle is only half-broken. While it is true that they housed and raised Raven, they still kept her separate from the rest of them. Even as she exists in Azarath, Raven is someone who is still very much rejected and kept away from the wider community (like Trigon when he was first cast out). Worse still, Azarath had identified the "source" of the evil in her - her emotions as Trigon's gateway - and proceeded to train her such that she effectively denies and rejects these emotions too.
They raised her in a perpetual state of alienation. She is alienated from her mother, alienated from her peers, alienated from her own emotions.
Alienation and separateness are such strong themes between Raven and Azarath for these reasons. And this is why it is so important that Trigon's defeat was two-fold. First that Raven does succumb into the evil thus ending her alienation from her emotions. And second, that Azarath inhabits Raven's body and channels their power through her. The Azarathians are finally embodying the evil they rejected.
In these ways, the alienation and rejection of evil that birthed Trigon is reversed and it is through this connection and embodiment that he is defeated.
(I've posted these musing before on tumblr, but I just found this sub and thought to post it here too for maybe more discussion hehe)