Who is Martin Silenus from The Rise of Endymion and what is their importance?

Martin Silenus is one of the original Hyperion pilgrims. He is the poet, who wrote the Cantos, a retelling of the Hyperion tale. He is now over 900 years old, and he spends most of his time in cryogenic sleep in his estate on Hyperion. He considers himself to be Aenea's adopted uncle.