To be perfectly honest, I think PST's ending sets it up pretty nicely for a sequel.
The Nameless One died and was recruited into a never-ending war, but as we know, he was pretty fucking powerful (especially now, after merging with other reincarnations). The ending doesn't state whether he lost his powers or not.
If he didn't, a force like him could tip the balance and make one of the sides finally win and end the war. Surviving the war, helping one of the sides win (or making both of them eradicate themselves), ending the war and escaping Hell would be a pretty decent premise imo.
You got it all wrong. Brave and stunning size+ Annah of color goes to HELL to show the white cishet archdevils who's the BOSS and rescue her hapless love interest, Nameless One (of color).
In the end, she helps him transition, abandon his Nameless deadname and adopt the name Laqueefa (they/them).