Buffy The Vampire Slayer

In episode 19, the Scoobies discover a spell that will give physical form to the First, allowing it to now be harmed. In the fourth act, a massive assult against the First occurs, it morphing into past big bads to do battle. In the end, the First is wounded and forced to retreat. The final moments of the ep, much like Lessons, end in the school basement, with a realization learned from the fight earlier. It is more than just the physical forms of the dead it takes...it is their complete essence. The concluding shot has the First, in the guise of the Master, walking to Principal Wood’s office, muttering an incantation. The Hellmouth begins to open.