u/Few-Marionberry674

NO, Sara dying and becoming Canis isn’t the canonical fate of Sara. It is a what-if scenario similar to Fallen Edelgard in Azure Moon and Fallen Rhea in Silver Snow.

I‘ve seen some people say that the attack on Ulster from Leif’s group lead to the death of every Thracia 776 character except for Leif, Nanna, and Finn, that isn’t the case. Thracia 776 takes place in-between and during the events of Genealogy Chapters 5 through 8, the Ulster raid is an events that happens in the story, and it leads to the remnants of Leif‘s army needing to be rescued by Seliph’s army (we see this from Seliph’s perspective during Genealogy Chapter 7).

After Leif‘s group is rescued and liberate Ulster from King Blume, he and Seliph agree to take on Manster and Canote respectively. So as the events of Genealogy Chapter 8 take place and Seliph’s army fights Ishtar for the first time and kills Blume for good, Leif’s army is taking on Reinhardt, Raydrick, and Veld simultaneously.

Should Sara survive the final battle, her epilogue states that she survived the Holy War and was placed under Leif’s protection after the war.

As I stated before, Canis showing up in feh doesn’t mean that Sara becoming Canis is the canonical fate of Sara, feh has already delved into the idea and usage of characters coming from alternate universes, this is just another example of that being the case, and people shouldn’t jump to conclusions.