Silenus was a follower of Bacchus. Susan and Lucy meet him when they were dancing with the Walking Trees. At the same time that they are meeting Bacchus and Silenus; Peter, Edmund and Trumpkin were meeting Prince Caspian.
Silenus has an amazing "power"; when he calls out for refreshments, grapes grow all over the place. He was mentioned when Narnia was free again and the Old Narnians became friends with the Telmarines of Telmar. He was known to be an old man that rode a donkey.