Ariel (also Arael, Ariael) : Angel whose name means "lion of God." Ariel appears in biblical, apocryphal, Gnostic, Coptic and occult literature in a variety of guises, both angel and demon.

The apocryphal book of Ezra calls Ariel an angel. In the Old Testament, the book of Isiah refers to Ariel as an altar, man and city. This was echoed by the Renaissance occultist Henry Cornelius Agrippa von Nettesheim, who referred to Ariel as a demon, angel or city. In Hebrew lore, Ariel is a name for Jerusalem, and in kabbalistic lore it is the name of a virtue. Ariel is ranked among the seven princes by Thomas Heywood in The Hierarchy of the Blessed Angels. In the Coptic Pistis Sophia, Ariel rules the lower world, and in Gnosticism he is associated with the creator god Ialdabaoth. In ceremonial magical texts, Ariel is described as a lion-headed angel.

Shakespeare named a fairy Ariel in The Tempest. Ariel also figures in Gaelic prayers of protection for the home and earth.
source for additional reading/information:

Davidson, Gustav. A Dictionary of Angels. New York: The Free Press, 1967.