Hassan the Undying was an Orion male living in the 24th century and early 25th century. He was a member of the Orion Syndicate, employed by Melani D'ian.

In 2387, Hassan assassinated Raimus on the planet Farius Prime. The person who employed Hassan was Melani D'ian, who herself took control of Raimus' portion of the Orion Syndicate.

In 2394, Hassan joined Melani on negotiations with the Klingon Chancellor J'mpok, where he was presented as being in charge, with Melani as his slave girl.

Following this, he moved his own base of operations to the former Orion homeworld in the Rigel system, where he could conduct Syndicate operations outside the Klingon Empire. This was presumed to be on the orders of Melani, who trusted him implicitly. (ST website: The Path to 2409; STO novel: The Needs of the Many)

By 2409, Hassan was running Syndicate operations on Nimbus III from a stronghold in the desert outside Paradise City. Around that time, he became involved with the Tal Shiar in a weapons deal for thalaron triggers and ran afoul of Starfleet and Klingon Defense Force officers. (STO - "Wasteland" mission: "Secrets of Nimbus") Hassan had turned a crashed starship into his personal stronghold and maintained a dance and arena fighting club, the Shangdu, inside. He was ousted from power by an Allied away team, whom he forced to fight in his arena. Hassan fled to his Warbarge-class ship in orbit of Nimbus III. Before the ship was destroyed by the Allied starship and a pirate fleet, the Undying attempted to escape with a shuttlecraft. He was captured by the Allies, however, and his sense of honor made him share his secrets. (STO - "Wasteland" mission: "The Undying")

The player has the option to destroy Hassan's craft instead of capturing him.
By apparent coincidence, his name matches the Orion naming style described in the FASA RPG - The Orions module: Book of Common Knowledge.
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