Glass only really works if its central figures feel like they belong to the same world even though they came out of different kinds of movies. Shyamalan pulls that off by letting each major character carry a distinct worldview into the story.
David Dunn
David is still the closest thing the trilogy has to a moral center. He moves quietly, thinks practically, and carries his burden with a kind of sad steadiness. In Glass, that steadiness is constantly challenged by institutions that want to define him downward.
Elijah Price
Elijah remains the great architect of the trilogy. He sees narrative shape where other people see chaos, and Glass belongs to him in a way that only becomes clearer as the film moves forward. Samuel L. Jackson plays him with fragility, pride, menace, and patience.
Kevin Wendell Crumb and the Horde
Kevin is not a single-note antagonist. Glass inherits the complexity of Split, where James McAvoy turned each identity into a different kind of pressure. Dennis, Patricia, Hedwig, and the looming Beast all bring different energies into the room, which keeps Kevin unstable in a way the movie can keep exploiting.
Casey Cooke and Dr. Staple
Casey gives the story memory and tenderness. She understands Kevin in a way nobody else in the film does. Dr. Ellie Staple, by contrast, is the great rationalizer. She does not want wonder, terror, or myth. She wants explanation, compliance, and containment.
That tension between believers, survivors, and managers is a huge part of what gives Glass its charge.
Another thing the film does well with its characters is refuse easy symmetry. David, Elijah, Kevin, Casey, and Dr. Staple all walk into Glass carrying radically different ideas about what power means. One sees responsibility. One sees design. One sees suffering as transformation. One sees survival through empathy. One sees every extraordinary claim as a problem to be neutralized. That clash of worldviews is part of what keeps the movie from feeling like a simple crossover exercise.