The Hupyrians were a humanoid species native to either the Alpha or Beta Quadrant. They had tight skin with a slightly scowling expression. The males were quite tall, often well over 2 meters tall, dwarfing their Ferengi employers, and even most other Alpha Quadrant species. They were especially popular with the Ferengi Grand Nagi, who used them as servants, food tasters, and bodyguards due to their strong devotion to service. So strong was their devotion, Hupyrian servants took a unique vow of silence which permitted them to only speak to their master, and for one to not show up to the funeral of their master was considered extremely unusual. (DS9: "The Nagus", "Prophet Motive", "Profit and Lace")
Since all Hupyrians seen were in service of a Ferengi, it is possible that their species were part of the Ferengi Alliance. Legends of the Ferengi by Ira Steven Behr and Robert Hewitt Wolfe mentions a conflict between the Ferengi and the Hupyrians.
According to Star Trek: Star Charts ("United Federation of Planets") and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), there was a star system named Hupyria (Tau Coronae Borealis), which might possibly be the system of origin for this species, in the Alpha Quadrant. This was a binary system with a a pair of K-class stars.
In The Ferengi Rules of Acquisition, the name of the species is spelled "Huyperian".
In the script of "The Nagus", Zek explained that he had faked his death using a Hupyrian sleeping trance taught to him by Maihar'du. In the episode this was changed to a Dolbargy sleeping trance, though it was still taught by his Hupyrian servant.