Leo is the Halliwell sisters' whitelighter, or guardian angel. He is there to guide the sisters throughout their many battles in the series. He also becomes Piper's husband

Cole is a demon who was originally sent to kill the sisters. He is half human, and ends up falling in love with Phoebe. Cole ends up becoming the Source of All Evil, and therefore is vanquished by the sisters.

Daryl is a human cop who assists the sisters when they run into legal troubles as a result of having vanquished demons who were wanted for murder.

Chris is a half withelighter/half witch who appears in Seasons Five and Six of the series. He at first appears to be shady, but it is proved that he is the son of Piper and Leo who has come back from the future to save his brother.

The original Source of All Evil (before Cole), a major demon who is intent on destroying the Charmed Ones. He appears throughout the first half of the series before the sisters find a way to defeat him.

Zanku appears in Season Seven and is an unstoppable demon. He is intent on destroying the sisters, until like the Source of All Evil, the sisters are finally able to defeat him.

The Elders are angels, similar to whitelighters, although they are above the whitelighters in power. The main purpose of the Elders in the series is to provide rules for the witches, which the sisters usually ignore.

Darklighters are the evil version of whitelighters. Their job is to lure people away from good and to kill whitelighters so that they cannot help good witches.

Throughout the series there are various demons that appear in each episode, including the Demon of Fear, Barbas (pictured above). The demons in each episode are the evil that the sisters must defeat in order to protect innocents and keep the balance of power.