C.S. Lewis had a big imagination, and a high regard for the occult. Combined, these make for a dangerous blend of Theosophy, pagan myths, and an unbiblical worldview. This video compares his views to the Holy Bible. Sadly, they do not match up.
(1John 4: Beloved, believe not every spirit, but try the spirits whether they are of God: because many false prophets are gone out into the world.