Shame the story is can't go with the mc keeping mostly human appearance wise, but since coming from tf ..
To few heroic fantasy around here, most go along reality or close to, while demons would be quite useful moral and life wise.
As, how do they get fed if nobody (can) work to produce then cook ?
R : conquest or if no option, lesser ones sent to the tasks.
Liked as story where the hero was sent looking why a border fortress did not respond anymore.
Once there and after quite some steps (getting new compagnons along).
Luck (..) Make they met with a food caravan getting raided, which is in dire need back at the fortress.
Thing being the fortress has a tear (as a reality one aka passage between worlds, not the best stability wise its power related ?) There join an undead army, about 10k the human locked in the fortress.
R : sabotage, conflicts etc. As the mc found (..) A book about relations and names its an done deal, killing one general and getting a succubus and her comrades along. Sadly the story did not go much further, knowing tears where opening at various locations, without very performing communication if they aren't on other non linked continents. Humanity would have it tough, but there is always a way.
TBS, the mc being the only one who can make good of the situation, knowing he has an unkillable + eternal army, outfitted by his dwarf and others ally's. Of course he has plenty to do locally as humanity and local religion don't consider non human as possibly good.
This said, its a good thing they are no science related to genetic as non human races have very to limited numbers at this time (after three wars, it could be to late, but he know of others lands where more of the Races lives.
Its not easy since that place is very much a wasteland, desert type.
On the mc party there is plenty of magic users (himself getting to use a custom (capacity wise) of dragon magic.
This since he is to old and tied to his sword to learn magic.
Add the dragon help by creating a bubble to close to stop time, so he can train).
The party otherwise get powerup, add custom equipment (material alteration, wow).
Etc. Options are endless in fact.