With apparent immunity to mutating radioactivity, cold, and poison, some say he fed off all three to become what he is or was.
Rarely seen though often heard, he would dart around the peaks up and down with two boards strapped to his feet, hollering and shouting and eating things smaller than him to grow his girth.
During some seasons of the moon, long silences would echo across the waste and those poor enough to have to occupy the space around the mountain on traveled roads, or to bandits hiding out using the mountain's legend as cover from being found, would note the silence and assume that Fast Snorlax was gone. Then, however unlikely, some time later his roars would be heard again, and the shuffle of his planked feet cracked from rock to rock, sending chills into whomever may hear his wails.
It is unknown whether or not he is part of the sprawl, or a revert that runs rampant on the mountain as a better suited habitat, or if he is simply a dude that likes doing what he does, enjoying his time being immune to the big cliff's perverse effects, living as a Champion of Rot.