So it’s not a mythosaur on Durge’s armor, just a likeness of his master, who happened to look similar to a mythasaur. That is some coincidence.Durge was already an aggressive and unique type of his species, he met up with Mandalorian battle master/warlord called Jaing - who trained him in the ways and methods of Mandalorians. Durge had by time used a suit of armor. Jaing was attacked and presumed killed by rival Mandalorian group, and so Durge vowed to wipe them all out in retaliation and revenge that kinda thing. Jaing was an unknown species, had a helmet or head the shape of the mythosaur.