Who or what is at the pavilion when Aslan arrives?

From the text:

The next thing they saw was a pavilion pitched on one side of the open place. A wonderful pavilion it was — and especially now when the light of the setting sun fell upon it — with sides of what looked like yellow silk and cords of crimson and tent-pegs of ivory; and high above it on a pole a banner which bore a red rampant lion fluttering in the breeze which was blowing in their faces from the far-off sea. While they were looking at this they heard a sound of music on their right; and turning in that direction they saw what they had come to see.

Aslan stood in the centre of a crowd of creatures who had grouped themselves round him in the shape of a half-moon. There were Tree-Women there and Well-Women (Dryads and Naiads as they used to be called in our world) who had stringed instruments; it was they who had made the music. There were four great centaurs. The horse part of them was like huge English farm horses, and the man part was like stern but beautiful giants. There was also a unicorn, and a bull with the head of a man, and a pelican, and an eagle, and a great Dog. And next to Aslan stood two leopards of whom one carried his crown and the other his standard.