Dax Fex Fize Gossimar Day Slitheen was a male member of the Slitheen family and is married to Bloorm Vungah Bart Gossamir-Day Slitheen.
Dax posed as Jay Stafford and attempted to avenge his family after their defeat by Sarah Jane Smith.
Dax, his wife Bloorm Vungah Bart Gossamir-Day Slitheen and Korst Gogg Thek Lutiven-Day Slitheen stole a technology from the Blathereen that made them able to use skin suits from slim humans. (PROSE: The Lost Boy)
Whilst breaking into his house, Maria and Alan Jackson discovered a body hung up, like a piece of clothing. After revealing this to Sarah Jane, they set off to stop Dax, Bloorm and Korst Gogg Thek.
After discovering the true motives of the Xylok, Mr Smith, Dax and Bloorm decided to help and they formed an alliance with Sarah Jane, Alan and Maria. Ultimately, Mr Smith's plan was foiled, and the three Slitheen left Earth. (TV: The Lost Boy)
