Exactly how Unit 34879721312 ended up on display at the Oddity Museum of Gehenna is lost to history; rumor has it that he was captured by a clever trap at the last Great Modron March 1000 years ago, before that entire race seemed to march off into oblivion. But for centuries the caged modron had been a popular favorite, as many had heard stories of the strange creatures that few of the currently living have seen. The Unit himself had seen no choice but to quietly accept his fate, as he saw no hope of escaping from his captors and returning to his duties on Mechanus. He would calmly answer questions and perform "tricks" for the visitors, as he could see no advantage to refusing, and pleasing his captors would gain him extra food and batteries.
His fate changed one day when a gang of interplanar thieves, led by the notorious Carlos of Vane, broke into the museum to steal valuables. In the modron's childlike innocence, when he saw the outlaws enter the museum and open his cage, he asked, "Have you been sent by Pentadrone 23898712 to recover me and return me to duty?" Carlos, being a quick thinker and natural bluffer, replied, "Yes, I have. Your orders are to follow my instructions until we reunite with the Pentadrone." The modron had no skill in sensing deception among humanoids, And thus his new life began.
Not sure what to do with his new pet at first, Carlos soon realized that having a blindly obedient 600lb metal friend with minor magical skills could be quite useful to a group of thieves and pirates. The modron, newly dubbed "metalbeard", became an integral part of the gang: his unique appearance would grab the attention of any witnesses, especially as the gang members talked up his "leadership" and appeared to be taking his orders, making sure they didn't recall details about the other gang members. And in the rare cases when a surviving witness got away, they could just store away the uncomplaining Metalbeard with the luggage for a few months until the heat died down. But gradually over the years, and after experiencing many bizarre and violent events in his career as a thief and gang member, Metalbeard began to actually develop some true free will and a bit of a personality of his own. And the inevitable day came when he realized he did not have to follow Carlos's orders.