Kijin

The oni race.

Once every few hundred years an elderly ogre can evolve into one. Their ability unnaturally high, they are often said to be capable of crushing the heavens.

The oni, can reproduce with any race, but choose not to. All their magical energy gets absorbed in the process, and some have not been able to recover it.

Many people have lost all their magical energy after naming monsters, and even Demon Lords generally avoid it.

There are two types of children produced by oni. The first are created with seed, the second is truly labored over. The former is made by combining some of one’s magical power, and while they do inherit some abilities, they tend to be weaker. The latter one pour all your strength into. But one’s lifespan is shortened as a result.