Like all good plot twists, it seems inevitable in retrospect -- Mother Om was trapped in the heart of her power, too. I really like the visual composition of this page and how it drives home the reveal. Every time we've seen Mammon up to this point, the composition has emphasized how huge and menacing he is, sometimes devoting an entire panel to an eye or part of a jaw. The final panel's wide shot, combined with his posture, makes him look old, shriveled, and tired. (Not that we, or Alison, should underestimate him.)
AHHHHHH like okay i still need them to super kiss at some point? but honestly this is almost better than kissing.
So a devil's form can vary based on their self-concept even if it doesn't alter their mask color? I suppose we saw that with Princess Mamoru Jaegermeister's original ebon shape.
also like............we're now one step closer to the Future Secret Allison from that one secret drawing, what with her face scars