Tangental to a saga on the Equestria Life roleplaying website, the diamond dogs were all but wiped out with a few remaining stragglers left in the entire world by a systematic series of events that left Equestria shaken.
Huski, leader of the Diamond Dog Mining Company, long ago ruined one of Celestia's plans. As punishment, he was made immortal and forced to serve her. He has since been pardoned but requested to remain both immortal and under Celestia's service. With the Princess mysteriously gone, Huski finds he is still immortal but no longer bound to a chain of command. Powerful villains laid claim to Ponyville and Huski depleted his race's military reserves and called in many favors trying to defend it, but ultimately it was conquered and nearly leveled, the Elements Of Harmony having moved on from each other and the town.
When an old colleague of Huski's took this chance to completely screw him over, he was forced to sit and watch as what remained of his people were bombarded into oblivion by a pony called Spark Lens, who was collaborating with a self proclaimed 'King Of Hell' in secret. With his people gone and his only two friends likely dead too, he made a deal with the Witch Queen, Hummingjoy, to get revenge on Spark Lens alongside the only five diamond dogs still loyal to him.
With a squad of flying dogs and a steel juggernaut backing him up, Huski sets out to Canterlot to board Spark Lens' stolen flying weapons platform and avenge his people.