It's CC0
If you are experiencing any issues with the assets feel free to contact me, I will do my best to fix it.
Thank you for bringing this issue to my attention.
Apparently there was a problem with the symmetry of the character. It should work now. I tested it with Mixamo and there were no problems. However, if you're still having trouble with something, let me know and I'll fix it.
I also exported the King and Death mesh without the sword and wings so you can upload it directly to mixamo without having to remove them yourself.