Onaga the Dragon King killed in the Lost Tomb in Sindel's Deception ending.
The Lost Tomb was an arena that was located in the Realm of Outworld.
Overview
This aged-old, pyramidal tomb contained the remains of the Dragon King's Army which consisted of loyal warriors who watched from the wings while locked in their stony prisons after they ritualistically commited mass suicide since his death. In the distance behind the Dragon King's sarcophagus was a huge, golden circular object with a striking representation of the Amulet of Shinnok. And what was written on the walls of this tomb as well on the king's sarcophagus is an ancient Edenian language inscribed by Onaga's holy men that was intended to bring back Outworld's long lost ruler from beyond the grave by returnng his spirit back to his original body.
In Mortal Kombat: Deception, Queen Sindel and her faithful Edenian knight Jade came to this tomb after escaping their peaceful, majestic homeworld of Edenia which was invaded and stolen by the newly resurrected Onaga and his Tarkatan armies with the traitor Tanya at his side. Sindel began translating the ancient dialect in hopes of defeating Onaga, but when the Dragon King arrived at his own tomb, he and his new puppet Kitana try to stop them. Jade fights them off and thus gives her queen more time. Sindel finished inciting the spell and Onaga's soul was replaced from Reptile's body to his own. She then thrusts her Kwan Duo into the heart of the corpse and screams the incantation. As the corpse came to life but cried in such angonizing pain, the spirit of the Dragon King was return to the cold sleep of death. The Saurian warrior's body and soul returned to his natural state. And Princess Kitana herself who was no longer under Onaga's control return to normal as Sindel has finally reunited with her daughter. The realms including Outworld and Edenia were liberated and safe once more from the threat of the Dragon King's new tyranny.