I wasn’t a big fan of ol’ Seteth but I didn’t really hate him, just a mild dislike for the character. He seemed so cold and almost ruthless, without a reason to do so.
He’s a high ranking member in the academy and in the Church of Seiros. Him and Rhea have a obvious loyalty to one another.
He actually joins a battle on a beach. I didn’t use him much but I wished I had his flying dragon.
We learn after the mission is over that he is really the father of Flayn, not her brother. And while I didn’t find out during my route in the game, he’s Rhea’s brother and a son of Sothis, the goddess of which the main religion is based and the same being that speaks to Byleth in ghost form.
Since I sided with Edelgard, I eventually faced him during a big battle.
He was actually pretty easy to defeat.
While I hated what I did to Flayn, I had very little pity for Seteth.