In the Prayer Book Baptismal Service, the candidates (or godparents on behalf of a baby) are asked if they “renounce the devil and all his works”. (1) In the Common Worship Service, the candidates (or parents and godparents on behalf of a baby) are asked:

“Do you reject the devil and all rebellion against God?”
“Do you renounce the deceit and corruption of evil?” (2)

The Devil

Before God made human beings he made the angels to be the first citizens of Heaven.  But among them were some who, though they owed their life and existence to God, would not have him as their King.  Their leader was an angel called Lucifer, the Lightbringer.  He wanted to be completely independent of God, to be on his own, and so there was no place for him in Heaven.  Instead he, with the other angels who followed him, came to this world to set up his kingdom here (Revelation 12:8,9).  Since then he has become known as the Devil, or Satan which means the Enemy.

The Devil is a spirit who is completely evil.  Only one thing concerns him, to make his kingdom as big as possible.  And so he spends all his time in fighting against God and in trying to replace good with evil in order to draw as many human souls as possible to himself and away from God.