Here's a simple plot overview for my challenge - A few ordinary teens living in a dark city (in the slums, subways, tunnels, sewers, etc...) with faeries and goblins and such living there too but in their world called OtherSyde. The teens come into contact with these creatures and get involved in an internal power struggle between an elf queen and one of her former vassels. The vassel tried to dethrone her. To do so, he got some guards to join his force to start a rebellion. A fight broke out between the queen and her knights and the rebels. Rebels lost. The evil vassal's spirit was sealed away by the elf queen, and the other rebels were exiled. Before he was sealed, the vassal declared to return and take what is his. Centuries later, the elves get wind of a rumor that the evil lord was reincarnated in a human body. One of the queen's knights appears to the teens, asking for their assistance in finding the vessel where the evil lord is imprisoned and taking it back to the kingdom before his spirit is revived.

Sorry if it's not the greatest summary. I'm in a hurry cuz I've got to go to work. But I will fix it when I get the chance.