The Jester is an alien lifeform who travels the universe. In this story he has come to visit the Earth, which he last visited a thousand years ago, when he spent his time in Ireland, where the locals worshipped him as a god and called him a Leprechaun.
He is called The Jester advisedly, because he is a jolly but mischievous character who likes to play tricks on people. He is not evil, he just likes having fun. Sometimes he makes dreams come true.