Well, Hades is the god of the dead and King of the Underworld. Despite his importance in Greek mythology, he tends to be frowned upon due to his mysteriousness and rare appearances. He and his demigod children are, on a regular basis, shunned in demigod society, yet this changes at the end of the Titan War, at Percy Jackson's request. He is a very cold god, normally not even caring about his children, but he only likes his only child, Nico, (seemingly). His cabin is built by Nico and his servants of the dead at the end of the Titan War. It is purely made out of solid obsidian with a skull over the door and torches that burn with green fire. The torches cannot be put out as they are protected by magic so they are lit twenty four hours a day, seven days a week. Hades is one of the Big Three but he used to not be counted as a Big Three, or even as an Olympian, and for eons, he hated his overshadowing brothers. You can learn more about Hades by reading the Percy Jackson books, especially The Titan's Curse and The Last Olympian, if you haven't already. I hope this helps!