Illusions
“Which is more dangerous? A powerful necromancer or a powerful illusionist?” To us the answer is easy, even a mid level illusionist can be far more dangerous than a high level necromancer. Necromancers are well known by most experienced players, and their strengths and weaknesses are common knowledge. However, many DMs overlook the very destructive power of illusion spells.
Illusions are essentially tools for the NPCs. Other than spells like Invisibility or Mirror Image, illusions very rarely have a use in a PC’s spellbook. Very rarely can they pass a silent image off as the real thing to a powerful villain, and even if they can it is rarely a threatening spell. However, spells that manipulate light are still a dangerous tool for the DM, and can be used to create a very challenging adventure. Imagine a room, filled with arrow slits from one side. The party walks in, and immediately knows that there is going to be an attack from that direction, and defend themselves accordingly. However, if you simply cover the wall with an illusion, disguising the arrow slits, the party thinks they have nothing to fear, and continue forward. Then, when the goblins fire their poisoned arrows through the wall, the effect is much greater, and even high level parties feel helpless.
Illusions can be used to realistically get your villain out of a room, without resorting to overused methods such as a Contingency with Teleportation. Often, using this escape, while it is effective, makes the PCs feel like they’re being cheated, and can even give the impression that your villain can never be defeated. However, if your villain throws his minions at the PCs, giving him two rounds to escape, he can run down a secret passage to safety. Naturally, the PCs will pursue, but say the escape rout has two exits. All the villain needs to do is cover the passage he used with an illusionary wall. Then, the PCs run into the wrong passageway, either to a dead end or whatever other traps you may have in store for them. Illusions can also give your villains a psychological advantage. For example, a few well placed illusions and fire spells, and a wizard can very easily make himself appear to be an ancient red dragon.
Pit traps, ambushes, the uses for illusions are unlimited. They can be used in almost any level campaign, to add an element of terror to any game. Clever use of illusions can completely throw off a group, and create a game to remember.