My general thoughts & opinions on them

Big fan of dragon dad who is desperately trying to appear as human brother! Mother hen to everyone from Flayn to Felix, casually talks to giant birds and turtles, writes kids story-- what's not to like?

Favorite moment of theirs

His entire attitude shift while Flayn is kidnapped always breaks my heart. That's why my favorite moment is the next chapter, when he organizes a fishing tournament just so Flayn can have all the fish she could ever want. In particular, I like this exchange:

Seteth: I have something to ask of you. Byleth: Leave it to me. Seteth: I have not even told you what my request is yet! Well, fine.

A close second is at the end of his and Flayn’s supports when they address each other by their Real names. They deserve to be themselves... :,)

Favorite support chain

Seteth and Bernadetta’s supports are just so sweet :3 Making a book together and Bernadetta basing Saint Cichol’s appearance on Seteth. It’s adorable~

My dream FEH alt for them

Seteth NEEDS a winter holiday alt. He’s a winter baby! You don’t get to celebrate his birthday in-game! It could not be a better match!!

Headcanons and/or ships I have

I like to think, in either a modern AU or an immortal modern setting, Seteth publishes children’s books as his main job instead of a side gig. It suits him <3 

As for ships, I’m a big fan of Male Byleth/Seteth but any Byleth/Seteth will do. Also Seteth/Jeralt. Shhhhhh...

Favorite art of them