Shiva is the god of destruction. His role is to destroy the universe in order to re-create it. He is seen as the source of both good and evil.
He has..a third eye (representing wisdom and insight); a cobra necklace (representing destruction and recreation; snakes represent this in the way they shed their old skin for new skin); vibhuti (three lines drawn across the face to represent his power); a trident (which represents the three functions of the Trimurti).