Storyline
In restarting the timeline, Liu Kang redesigned the destinies of many kombatants he once knew. In doing so, due to creating a more benevolent Outworld under Sindel's rule, Onaga never obtains the throne as he did in the original timeline and as such, Shao Kahn never interacts with the Dragon King to the full extent as he did in previous timelines.
Mortal Kombat 1
Onaga exists within Outworld far away from Sun Do and its inhabitants. He is regarded as one of the most powerful, non-deity beings in all of Outworld. Only a few kombatants have encountered and faced the Dragon King and lived to tell the tale, this being General Shao's ancestors, who imprisoned the Dragon King within Mount Tsaagan in Outworld to prevent his destructive nature from bringing ruin to Outworld.
After attempting to usurp the Outworld throne from Sindel, General Shao and his subordinates are imprisoned for treason. Despite this, the General and his men eventually escape, regrouping to attempt to seize Outworld again, this time from Mileena, Outworld's newest and current Empress. In desperation, the General dispatches Reiko to free Onaga as a last resort. Although the task is near suicidal, Reiko follows the General's commands and confronts Onaga in Mount Tsaagan to tame the beast and release him onto Mileena's benevolent Outworld.