Source: Isles of the Shackles, pg(s). 8
Endymion is a fan of traditional Chelish opera, and the town boasts the Shackles' only opera house, the Three-Horned Hall. It is not clear whether the other residents share his passion for the arts, but those seeking the pirate lord's favour make a point of sitting through performances.
The city takes its name from the numerous imps which live in the area. Endymion is a mutineer from the navy of Cheliax, and is worried that some of the imps may be Chelish spies. As a result, he has recently started trying to eradicate them. Ethnic Chelaxians (apart from members of Endymion's own squadron, the Devils' Own) are not welcome in the town, for the same reason. Any who arouse Endymion’s suspicions are thrown into the city’s prison. 
Pirates established the port town of Hell Harbor in the early years of the Shackles, as the natural harbor is deep and easy to defend. They used limestone from ancient quarries and Ghol-Gan ruins to build tall watchtowers flanking its narrow harbor entrance.