I like the idea of a soft-spoken antagonist, he doesn't need to raise his voice to inflict terror on those who oppose him. He's outwardly friendly and affable and has this cult of personality, but truly a sociopath underneath. He's somewhat like Kae'Kil in this way, which is probably why Serinth ends up dating Kae'Kil, she had daddy issues. Heyoke is soft-spoken in the same way, just not an asshole, he looks a lot like his father though.
As Serinth explains to Heyoke during the fetus graveyard scene, people are surprised when they discover how much the children despise their father, but they don't see the monster underneath the fur.
Because of the dilution of bloodlines after each generation due to the Rot, perhaps Mosphet's children are only expected to live half as long as him.