Kill Billie Vol. 2

The Charmed Ones kill a few Young Turks. Two of them, Nomed and Zohar, watch the scene with great interest; they keep sending him other demons to battle the sisters in order to know why the Halliwells are hiding in the Underworld. Nomed and Zohar know they must find a way to gain power over the Triad, who keeps resurrecting, if they eventually want to rule the Underworld. They will need help, Charmed help. The demons think they can get the sisters to help defeat the Triad as they know the Halliwells want their old life back (writing Ask Phoebe, raising Wyatt and Chris, starting life with Henry). The sisters will have to go to a "dark place" in order to battle the Jenkins and whoever is helping them, and will need to summon The Hollow. Victor takes care of his grandchildren. A ghostly Leo appears to Piper. Elise and Coop also appear. Source: SpoilerFix.com

[Leo] will be back for the final two [episodes]. Source: Ask Ausiello @ TV Guide

Brad Kern reveals: My plan is to cut up a two-parter where episode 21 crests to the big season finale-like battle, but then repercussions occur and that leads us into the series finale. They'll be separate episodes, but one hands the baton off to the other. Source: TVShowsOnDVD