User blog comment:B214/Volume 23 discussion blog/@comment-81.135.250.239-20170404163037/@comment-10330822-20170405113551

Except Greek mythology there is a distinct difference between Death and Underworld. Hades doesn't control the concept of death, he rules the underworld. Thanatos is the god of death that brings death to others, while Hades is the one who rules all that dies.

That is part of the reason Zeus, Poseidon, and Hades are considered the higher gods of Olympus, because Zeus was had dominion of the heavens, which included Olympus, Poseidon controlled the seas, and Hades controls the Underworld.