And the shoot 20 Evilkin runners achievement has a shield shredder picture. Some of the pictures are just there because they wanted them there. Doesnt have to have a rhythm or a reason.
Well there's enemies that look like mini shield shredders in the game so maybe they are Evilkins
Maybe the Chapters all tie into each stronger than previous and the Adventure Packs are really levels with ties to another.
Also, regarding Mesmeralda, I feel like she and Vathek and other previous villains would probably be better suited for Adventure Pack captures. Say they rejig Dragon's Peak to allow capture of Vathek OR Nightmare Express/the Mirror thing is like a "Greatest Hits" of the villains.