Objects Are Closer Than They Appear
Setup
After retrieving any needed spell components from the Magic Shop (and possibly running into a group of controlled townspeople), the group rushes to confront the Big Bad and prevent the opening of the Hellmouth. But first they have to deal with the ol' switcheroo, vampires (of course) and one too many Englishmen.
Action
The Ambush: Once the group decides to head for the Hellmouth, whether under Giles/Ethan’s direction, or by interpreting the dream and other clues indicating the importance of that site, the demon follows and sends a handful of real controlled townspeople against them. This is to slow them down, and give them a false sense of achievement, before the trap is sprung.
Suggestions for those to include are Graham (along with any Initiative Commandos still available on the surface), and minor recurring characters such as Jonathan Levinson, Devon (the Dingoes lead singer), and Percy. Drop the number to two or three if the whole group is not there (say if Buffy and Spike decide to patrol while research is being done), or if time is dragging on. This is meant to get the group jittery, and to lay groundwork for the scene at the end.
School Daze: Once past this initial threat, which should be dispatched fairly easily, the group has no problems reaching the burnt-out school. Once there, they find the way barred by an even larger group of townsfolk, nearer and dearer to their hearts. Of course, though it appears they face Joyce Summers, Tara Maclay, Shelia Rosenberg, Harmony Kendall (a different vampire disguised as Harmony, unless the gang is doing poorly, in which case it might be the real Harmony, and Spike convinces her to help), Xander’s folks and others (including ones used earlier — Parker, Jonathan, etc.) — these are all really vampires disguised by the demon’s magics. There should be two each for Buffy, Spike and Riley, and one each for the others.
Giles/Ethan directs the others to engage the folks and keep them out of his way while he prepares and starts the ritual to keep the Hellmouth closed — "and be sure not to harm them!" The Nevlock demon is close by, powering the illusions, cloaked mostly in shadows (or possibly as another one of the townsfolk, if the group is doing badly—have one of the cloaked vampires be the demon, and when it is taken out, so are the illusions).
In the close confines of the school, the demon can be spotted with an extended Notice task (that is, several Notice rolls over several Turns) garnering ten Success Levels over several Turns. Those engaged in combat can also keep an eye out as a "free" extra action (in addition to any combat actions) for an additional - 2 to all actions that Turn. Success indicates something "wrong" with the shadows in one corner.
If grabbed, the demon feels slippery and only semi-solid to the touch, but this doesn’t help it avoid attacks — that’s just part of its nature. If the Twilight’s Embrace spell is used, and it works too well (and the players are having too easy a time of it), the encounter may be enhanced. As the illusions start dropping, have the sphere of darkness extends out over them, requiring Notice rolls to "listen" for the enemy before attacking (at a -2 penalty, to both sides, of course!). If killed, the Nelvock rapidly oozes away into nothingness.
After a bit, Anya or Willow can determine (with an Occultism roll) that the ritual Giles/Ethan is intoning is the one of unlocking, not closure. If the group turns against him, Giles/Ethan attempts to take refuge behind the mass of vampires (if any) remaining. If the demon is defeated, or has his power blocked by darkness (or is otherwise revealed), Ethan uses his Ace in the hole — Giles.
He has Giles trussed up over the Hellmouth itself, out of sight of the scene of the battle, held upside down with a rope by a vampire with orders to drop him in at the climax of the ritual, or if things go badly. Ethan bargains for his freedom with this knowledge (he can also use this to entice the group to go to the Hellmouth if they discover him too early, escaping when the vamps attack).
Given the chance, of course, he’ll just slink out in the last stages of battle if it’s going against him, using whatever Drama Points are necessary to ensure his escape. If the group captures him, Graham and the other Initiative boys show up to take custody.
