Speaker
Very little information about the speaker is offered—they are given no name, nor any other identifying information. Instead, the poem is largely externally focused, taken up with vivid and relentless imagery of Byzantium. However, we can infer a great deal about the speaker from what they choose to focus on. This is especially true because so much of the poem's imagery appears to come from the speaker's own imagination and associations, making it especially revealing of the speaker's mental processes. What is clear is that the speaker has an almost feverishly active and imaginative mind, which is consumed by the themes of the poem: transcendence, art, and the boundary between life and death. The speaker also is identified with the poet to a degree, as revealed in the work's final line, wherein Byzantium is identified as a site of poetic inspiration.
The Emperor
The Emperor is one of the only individual characters mentioned in the poem, though he never actually appears to the reader. Instead, he exists in the background as a kind of overarching power in the city of Byzantium. The city's sleeping soldiers, its pavement, and its smithies are all identified as belonging specifically to him. This is based on historical reality, since the city of Byzantium—today's Istanbul—was the seat of power in both the Byzantine and the Ottoman Empires. The Emperor's presence therefore calls to mind the real importance of this city, linking the poem's vivid scenes to the long-ago world of ancient Byzantium. At the same time, the Emperor is a representative of human power structures, in contrast to the eerie, supernatural power of Hades.
