Mr. Tumnus is the first character Lucy meets in Narnia in The Lion, the Witch and the Wardrobe.
After Lucy steps through the wardrobe, she finds herself in a snowy wood and encounters Mr. Tumnus, a faun carrying an umbrella and parcels. He invites her to tea in his cave and explains that she is in Narnia, a country ruled by the White Witch.
Tumnus initially intends to report Lucy to the Witch, whose rule has made it “always winter and never Christmas.” Instead, he changes his mind and helps her escape, beginning his role as one of the story’s earliest sympathetic Narnian characters.
Readers sometimes answer Aslan because he is the book’s best-known figure, but Lucy does not meet him first. Mr. Beaver and Mrs. Beaver appear later, after Lucy returns to Narnia with her siblings and encounters the talking animals.