Heracles was a demigod as well with the strength of the his father the king of the gods, Zeus, but he lived a very long time because he achieved immortally. There was also the demigod Achilles that was bathed in the river Styx, which made his body impervious to injury accept for his heel which the river didn't touch.

I deal with these beings back home, Smoker. I know how dangerous they can be.