They were looking for help against their hereditary enemy, France.

Would she want to escape with him even if she had the chance, to live among the hereditary enemies of her people?

Some of them looked excited, happy with the thought of killing their hereditary enemies.

I've studied the histories and lore of my hereditary enemy.

That could be a serious complication for hereditary enemies.

On the other hand Bolgani was his hereditary enemy.

She cried to her hereditary enemy: "Will you kill me, then?

Why should Billy put himself at risk for the sake of his hereditary enemies, whether he'd helped to bring them up or not?

He knew none of his hereditary enemies were present,- but he was aware that they'd been there.

Seldom did a female of their hereditary enemies fall to the lot of a green man.