What are the Images of the Holy Spirit?

How does one "describe" the Holy Spirit? The Third Person of the Trinity is "pure spirit" and did not take flesh to become one of us. So, one uses images to help with the understanding of the Mystery of the Blessed Trinity..
In talking about the Baptism of Jesus in the Jordan, all four Gospels use the image of a Dove descending from the heavens and coming upon Jesus.
	Luke compares the Spirit to Wind and Fire.
In John's Gospel, Jesus himself uses the image of an "Advocate" (in Greek, "Paraclete") which means someone called to be permanently at our side, on our side, like a best friend or a band of brothers. References also include the images of Comforter, Counselor or Helper.
Paul uses the image of a "Pledge" in the sense of an assurance of more to come. He sees the Spirit as the beginning now of a share in the fullness of life, which comes after death.

Sources: Bishop Ken Untener, The White Book, 2008, diocese of Saginaw Catholic Answers, http://www.catholic.com