Dathan, also known to the Sith Eternal as "the Abomination," was a human male hybrid strandcast genetically engineered by Sith cultists on the planet Exegol in 12 BBY. The Sith cult utilized the template of Darth Sidious—the Dark Lord of the Sith and Emperor of the Galactic Empire—to create cloned vessels for the preservation of his essence. The strandcast who became known as Dathan was a byproduct of the cult's experiments, however he lacked a strong connection to the Force, despite his genetic connection to Sidious, and thus was deemed a failed experiment by his "father." Although Dathan was treated by Sidious with disdain for his powerless nature—being referred to as a "useless creature"—the excellent health he possessed nevertheless made him permitted to live as a means for continuing the Palpatine bloodline.
For his father's neglect, Dathan ultimately rejected him and the ways of the Sith in a similar fashion by escaping from his homeworld, intent on pursuing a life away from the dark side of the Force. He eventually married a woman named Miramir, who gave birth to their daughter Rey in 15 ABY. Unlike Dathan, Rey was strong with the Force, and so was deemed a viable host for her grandfather's essence. Determined to claim his granddaughter at all costs, Sidious sent the assassin Ochi of Bestoon to find and bring Rey to Exegol.
Dathan and his family settled for a time on the planet Jakku, where he and his wife struggled to survive in the desert as junk traders during the New Republic Era. They were kidnapped and impaled by Ochi with a knife in 21 ABY, though not before Dathan and Miramir hid their daughter by leaving her behind with the junk boss named Unkar Plutt. Rey remained hidden on Jakku for several years before discovering her dormant connection to the Force, which in turn led to her path to becoming a Jedi.