The narrator asks the reader to imagine spending one’s whole life in a dark dungeon and then stepping out one spring day into a world that’s bright, with sparkling suits of armor and bright copper pots. Readers should also imagine that just as Chiaroscuro steps into the light, Despereaux is born. The two will meet much later. For now, Roscuro is just delighted to be in so much light. He decides he’ll never return to the dungeon or torture another prisoner. He belongs up here.
Again, the narrator encourages readers to feel empathy for Roscuro—the change he’s making as he leaves the dungeon is huge, and the narrator suggests it’s transformative. For now, Roscuro feels like the light, bright upstairs is where he belongs. In this way, he’s not acting or thinking like a true rat (per Botticelli), which suggests he may not find what he's looking for upstairs.
Roscuro wanders from room to room until he gets to the banquet hall, where King Phillip, Queen Rosemary, the Princess Pea, and some nobles are dining. Roscuro has never seen happy people, and he’s enchanted. The princess especially is beautiful; her sequined gown glitters, and her laugh seems to make things glow. Roscuro is certain now that light, not suffering, is the answer to everything. He invites himself to the party.
The Princess Pea herself is almost a literal beacon of light and goodness, given how glittery her gown is and how good and kind she is. That even Roscuro recognizes how good the Pea is—and admires her for it—shows that he has something in common with Despereaux, a mouse whom Botticelli suggested Roscuro should scorn.