Son was the name of a shapeshifting male humanoid depiction of the dark side of the Force who was part of The Ones, a family of powerful Force-users living on Mortis during the Clone Wars. After the arrival of Jedi Anakin Skywalker, Obi-Wan Kenobi, and Ahsoka Tano, the Son tried to murder the Father and escape from Mortis. He also tried to recruit Skywalker, first by posing as his dead mother, then by direct demand. When these efforts failed, the Son infected Tano with the dark side to use her as a hostage to control Skywalker.
When the Jedi tried to use the Dagger of Mortis to kill the Son, he stole it and tried to kill the Father, but accidentally killed his own sister instead. Finally, by showing Skywalker visions of the heinous acts he would commit as Darth Vader, he managed to gain the Jedi Knight's allegiance, only for Skywalker to have his memory erased shortly after. When he tried to murder his father yet again, the Son was horrified to witness the Father impale himself. As he knelt in shock, the Son was fatally stabbed by Skywalker, and died in his father's arms.