Kudamat was trapped within Godfell Mountain, or rather, the mountain was formed around him when the Forgotten Gods lost to the New Gods at the end of the Earliest Age. Ever since, like many of his kind, Kudamat was forced to wait for the day he could finally break free. But it wasn't a simple burial the New Gods performed. To trap the First Doom, the usurper gods split part of his being into nine pieces and tasked nine mortals with hiding the soul shards so Kudamat could not reach his full power.
But they should not have given such a paramount task to mere mortals. The nine riders took the shards as far from the mountain as they could manage and buried them in the arid earth, but it wasn't far enough. Over the centuries, Kudamat reached out through the dirt and stone, veins of crystalline essentia stretching out like tendrils to find his missing pieces. Over time, the godly strife of the Earliest Age and the hidden resting places of the soul shards drifted out of memory and into stories and legends. Legends most sensible folk ignored or forgot.
When Kudamat found the first piece of his soul, he began channeling its power to restore his godhood, and a single thundering quake tore a fissure through the center street of Wyllin's Gulch — a terrible earthquake, they believed, not understanding the apocalyptic toll ringing out across the sands. Kudamat then used a fragment of his divine might to craft a colossus and droves of accompanying aberrations that would guard the soul shard while he siphons the remainder of his power and seeks out the other eight shards. Even with only the barest portion of his power restored, Kudamat's reawakening is all but inevitable. He grows stronger by the day, searching out the remaining pieces and building more colossi to guard them. If left unchecked, he will reclaim the power of all nine shards and break his earthen shackles, rising again to bring doom to this world.
Source · Drylands History