I picked the Deers as my cousin picked the Eagles. I think Claude has the purest path (in terms of ideas) because as it turns out he's half-blooded and he really wants to fix Fodlan for the sake of his heritage. So to do that, he wants to break down the walls and make Fodlan open, while he goes home to take the throne and make a bridge to both sides and make a new start with both countries....WHILE EVERYBODY ELSE JUST RIPS EACH OTHER TO SHREDS! Rhea is still alive but gets wounded by the tech missiles and it somehow wakes up Nemesis and you fight him as the final boss (I shit you not, Claude doesn't even land the final blow to him as his arrow makes an opening for you). In the end, you take up leadership for him as he goes back to take up leadership elsewhere in the promises of you two linking together both countries someday. For those wondering if he can be gay, NOPE, straight as a nail, so if you want to marry him in the end pick female Byleth.