Any ideas for a Seth build?

I know he's not ideal, but I got two 5* Seth's today and a 4* while pulling for our boy on the CYL banner (plus a 3rd 5* level 40 Seth). Basically, IS is telling me I should invest in this dude, so I wanna try to make a halfway decent build for him...

The IV options I have at the moment are:
+Def, -Spd (already lvl 40): +Res, -HP : +Atk, -HP for 5 stars and +HP, -Res for the 4*

I was thinking of sticking with the +Def, -Spd one and give him a Brave Sword+, Bonfire, Death Blow 3, and Swordbreaker 3 (c skill and assist are variable, I'll have to check what I need the most right now)

Any other thoughts? I don't necessarily want to build him as a Stahl 2.0 but rather something fun