Hades ruled the underworld. The underworld was the where you went after you died, there were different places in the underworld, some places you went when you were a hero, and some places you could guess who went there.
Hades wasn’t in charge of death, he was in charge of assigning the dead a place to live. He was the only decision maker in the Underworld. It was not very smart to annoy Hades whether you were dead or alive.
Hades had a faithful and deeply loved companion, his three-headed dog, Cerberus. Hades came to the surface now and then, to give his dog a sniff at a new place.
Hades attended council meetings of the gods on Mount Olympus.
He never thought of Mount Olympus as his home though. Hades had two powerful brothers (and three sisters) - the mighty Zeus, king of the gods, and Poseidon, lord of the sea; he also had several nieces and nephews.
His family thought Hades would never fall in love. Almost every person he met was dead. To everyone's surprise, one day, while allowing his dog a sniff at the surface, Hades fell in love. That's when the trouble started.