Summarize Arthur's dreams. What might the overturned chair and serpents symbolize?

The existing stories of King Arthur were rephrased by Sir Thomas Malory. He actually incorporated the original events in his book which had happened in the life of English and French kings. During the 15th century he had written 'Le Morte d Arthur'. He did not invent or discover any Arthurian stories but he collected all the stories that already existed and compiled it into one book.

In his story Arthur first dreamt that he was sitting on a throne over a pit and it was surrounded by venomous snakes and wild beasts. The wheels of his throne turn and he drops into the depths.

This is a prophetic dream, a vision which King Arthur had that suggested that he is going to face his death and that his empire' befall.

if i remember correctly king Arthur's dream was to unite his people back under to one body.

and im not sure about the second question about the serpents