John Keats
The poem is a personal reflection by the speaker, John Keats, on his own experience of reading Shakespeare's tragedy, King Lear and his emotional response to the play. Naturally, Keats portrays himself in a positive light. He shows himself as a sensitive and introspective man who is deeply affected by the world around him.
Throughout the poem, Keats describes his own reactions to the play. He is particularly affected by the tragedy and suffering of the characters in Shakespeare's King Lear. He describes himself as feeling overwhelmed by the "barbarous" nature of the play, which is incredibly violent, and the way it exposes the brutal realities of human existence.
William Shakespeare
William Shakespeare is the author of the play which Keats reads, titled King Lear, and his influence and artistry are evident throughout the work. Keats is also deeply affected by Shakespeare's artistry and his work, which profoundly impacted Keats' life and his own work. But Keats himself and Shakespeare are the only two characters in the poem.