WELL Nico's dad is Hades. He is pretty much literally the son of Death. He summons ghosts often and he can rip a rift in the Earth and summon skeletons straight from the Underworld. Even humans get the iggidyboogidies from him, his aura just freaks people out. He also practically lived in the Underworld before Camp, which isn't exactly like Hell, but it pings as dark and dead and decidedly NOT GOOD. So do what you will~ He's half human, half Greek god, making him a demigod/half-blood. Very mortal though.