The Seer foresees that the son of Phoebe and Cole will be very powerful, and The Source, who possessed Cole's body, must bring him to the evil side marrying Phoebe in the dark way, i.e., in a cemetery with a dark priest and drinking the bride's blood. Cole sabotages the wedding and The Seer releases a Lazarus demon that resurrects when destroyed unless buried in a cemetery to force the ceremony to take place in a cemetery.
"Marry-Go-Round" is a great episode, with Cole totally possessed by The Source. His despicable spells succeeds and evil wins this battle. Coolio is very funny performing the Lazarus Demon and The Seer is the most Machiavellian character of this series. My vote is eight.
Title (Brazil): "O Casamento" ("The Wedding")