Which C.S. Lewis novel features the character Puddleglum?

The Silver Chair is the C.S. Lewis novel that features Puddleglum.

Published in 1953, The Silver Chair follows Eustace Scrubb and Jill Pole after Aslan sends them on a mission to find the missing Prince Rilian. Their guide is Puddleglum, a Marsh-wiggle whose gloomy predictions conceal courage, loyalty, and practical wisdom.

The travelers journey through Narnia and the Underland, eventually confronting the Lady of the Green Kirtle. Puddleglum’s resistance to her enchantment is one of the book’s best-known scenes: he stamps out a magical fire despite severe pain and reminds the group of the real world beyond the spell.

Puddleglum is sometimes associated with other Narnian companions, but he appears specifically in The Silver Chair. He is not a dwarf, faun, or talking animal; he is a Marsh-wiggle, a distinct Narnian people.