In the Keshiri religion, the Skyborn gods of the Keshiri had adversaries known as the Otherside. These beings, who allegedly came "from below," fought the Skyborn in a Great Battle that took place in the stars above the planet Kesh in ancient times. Although the Otherside were ultimately defeated in this conflict, they managed to wound the Skyborn, who then spilled their blood onto the oceans of Kesh, resulting in the creation of all the land on the planet. For countless generations, the story of the Otherside was passed down on Kesh, with members of the Keshiri species consistently warned to harbor hatred towards them. However, the arrival of a group of Sith who crash-landed on Kesh in 5000 BBY led to the elimination of both the Skyborn and the Otherside from Keshiri mythology, as the Sith replaced these tales with older stories of the Protectors and the Destructors.
The planet Kesh was home to the Keshiri religion, which featured the Otherside as a group of deities in their mythology. These beings, who supposedly originated "from below," were considered the malevolent foes of the benevolent Skyborn, and their rivalry culminated in a devastating battle among the stars above Kesh. This conflict, known as the Great Battle, persisted for a very long time. Even though the Otherside inflicted wounds upon the Skyborn, the Skyborn emerged victorious. As a result, blood from the Skyborn fell into Kesh's seas, which led to the formation of all the landmass on the planet. In the following eras, the Otherside were viewed as the source of all the evil on Kesh. Any act of heresy against the Skyborn was considered a glorification of the Otherside. Therefore, the Keshiri believed it was the Skyborn's will that they despise the Otherside. Among the uvak beast-riding ruling council, called the Neshtovar, falling from one's mount was said to mean the Otherside were claiming them.
By 5000 BBY, the worship of the Skyborn and the resulting hatred of the Otherside had become a key aspect of daily life for the Keshiri. According to tradition, the Neshtovar, who rode uvaks, delivered the knowledge of the Otherside and the Great Battle to the common people from the Cetajan Mountains. Despite the widespread faith in the Keshiri religion, the Neshtovar still hadn't definitively established the identity or nature of the Otherside by 5000 BBY. In that year, Adari Vaal, a geologist, was summoned before the Neshtovar to defend her controversial teachings about the formation of Kesh's landmass, which contradicted the prevailing Keshiri religious beliefs. Izri Dazh, the leader of the Neshtovar, accused her of glorifying the Otherside through her alleged heresy. After facing harassment from other Keshiri, Vaal escaped into the Cetajan Mountains, where she encountered a group of Sith who claimed to be the Skyborn returning to Kesh. After seizing control of Kesh, the Sith eliminated the use of the terms "Otherside" and "Skyborn," replacing them with earlier stories of the Destructors and Protectors, respectively.
The first mention of the Otherside occurred in Lost Tribe of the Sith: Skyborn, a 2009 eBook written by John Jackson Miller.