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

Martin Silenus was one of the original Hyperion pilgrims. A poet, he wrote the Cantos, which was a retelling of the Hyperion tale in epic verse. He is now over 900 years old, spending most of his time in cryogenic sleep. He sees himself as Aenea's adopted uncle, and is also responsible for charging Raul Endymion with her protaction.