Further, Tolkien uses Musti to introduce a depth of characterization to his narrative. Musti is a mystery, and readers wonder who or what Musti really is. Is he merely a dog that just happens to be magical? Or he is something else that just happens to be in the form of a dog? Where did Musti get his powers? How does he know how to exercise them? How does he communicate with Kullervo? These tantalizing questions tickle readers' minds and engage them with the character of Musti and the story itself. Moreover, Musti's demise adds an additional element of character-driven tragedy to Tolkien's story. When Kullervo falls over the dead body of the hound, most readers' hearts probably skip a beat or two. How can the powerful, magical Musti die? Was he killed by Kullervo? What will Kullervo do without him? With his last companion gone and no guidance or further protection (even from himself), Kullervo meets his death and follows Musti to his tragic end.
In Musti, Tolkien recognizes a prime opportunity to exercise his vivid imagination and make the story of Kullervo his own. Musti, who receives the barest mention in the original Kalevala, becomes an intriguing central character in Tolkien's version of the tale. The hound enhances the plot and characterization of The Story of Kullervo and also offers a choice example of how Tolkien embraces tradition but also adds to it and shapes it to meet his own narrative needs and imaginative inclinations.