I believe that Rigor Mortex used to be a monster that Zehlam and his crew somehow transformed into the Rigor Mortex we know. And what other monster would turn into a gigantic, skeletal mirror than a Devil Glass! So that’s kind of what I thought of when I drew this.
So back when Rigor Mortex, Leonyx, and the Baboon Beast were all young... we have Leonyx meeting Rigor Mortex for the first time, before Rigor Mortex was turned evil by Zehlam and the others. And the Baboon Beast doesn’t want any of that attention, but still feels resentment towards Leonyx and Rigor Mortex. I guess for being happy. Because he really is that angry, even at that young age.