Board Thread:Questions and Answers/@comment-5618861-20160815190434/@comment-29602226-20160818101920

An incubus wouldn't spontanously learn spells, only the potential to cast more powerful magic once he learns to do it.

He would gain stamina, endurance and resilience. Even if his muscles don't become stronger on their own, he could put his body under way more stress than a regular being without negative consequences (plus sex with his wife would heal all training injuries), so he could become stronger quite fast.

And if his wife is the type who likes strong guys, he will probably become stronger even without training.

I don't know if he could go above normal human limits. As I said, we don't know how strong can regular humans become.

There are some Mamono, like the Wendigo, who change their husbands into monstrous/superhuman shapes.