The origins of these priests' master teachers explained as they've once believed that the long lost, true Emperor of Outworld was a bringer of order and civility since Onaga was a powerful military commander which already made their home of Outworld into both a unified, perfect realm and a majestic civilization for thousands of years long before he was betrayed and poisoned by his former advisor Shao Kahn who then stole his throne from him.After the king's death, they hid the last dragon egg, and kept it out of harm's way. His holy men then first participated in 'blessing' the Dragon King's own army at the time of their ritualized mass suicide pact within his tomb where they were mummified to await for his second coming. They then took the egg with them and traveled to far away lands of Outworld in search of an approperiate location to house the Great Dragon egg. The first area of their choosing was the old Sarna Ruins, but because of this land's increasingly unstable conditions, they were forced to locate the egg elsewhere. Traveling far and wide, they finally found this volcano and its hollow, molten caverns as the right location to house the Great Dragon egg. They've made a solemn vow that they and those they passed knowledge onto, would forever protect and care for the egg until the day of its hatching. They foretold that the birth of the baby dragon will be the rebirth of the Dragon King who will return to reclaim his former empire, and restore Outworld and its people to its former glory.
Meanwhile another sect of Onaga's holy men the same motive and reason have devised the means of bringing him back to life by returning his spirit to his original body, using their ceremonious magic spell fluent in an ancient dead Edenian language they have incorporated into it. They (with the help of Hornbuckle) even once captured the firespawn Blaze and corrupt his original design which pleases their brothers at the Lava Shrine to force him in help watching over the dragon egg.
After many years of their services before they died along with their descendants and acolytes, Onaga's holy men's foreseen dream have finally been achieved and their ancient prophecy have been fulfilled: The Dragon King had returned...
The Lava Shrine Priests are the polar opposite of the Shadow Priests, royal servants of their king's betrayer and sworn enemy Shao Kahn.