(Part 2 of a series, which begins with Spells that can ruin adventures.)

Third edition Dungeons & Dragons added the Scrying spell, which unlike Clairvoyance and Clairaudience could target a creature rather than just a familiar location. Scrying worked in conjunction with Teleport to make villains vulnerable to the scry-buff-teleport system of ambush, also known as scry and fry.

The target of the Scrying spell gets a save, but the wizard can always wait for another attempt, or just scry Igor or minion #3. The game offers a couple of eighth-level, defensive spells in Screen and Mind Blank. Will the Dark Lord mind blank Igor too? None of these spells can be made permanent, so apparently, every high-level villain needs archmages on staff just to thwart do-gooder knuckleheads who can cast a sixth-level spell. In practice, the best defense might be a DM with the chutzpah to fudge an improbable number of saves. The Pathfinder system makes the spell easy to counter with lead shielding. Why didn’t Gary Gygax think of that? He did. In the first edition, metal sheeting blocked Clairvoyance and Clairaudience.

The teleport ambush worked so well, and the game offered so few countermeasures that Monte Cook stepped up in 2001 and included spells like Teleport Block, Teleport Tracer, and Teleport Redirect in his Book of Eldritch Might. In 2005, the Spell Compendium finally added practical countermeasures to the base game with Anticipate Teleportation and Greater Anticipate Teleportation. These spells delay the arrival of teleporting creatures into an area long enough to foil an ambush.

Anticipate Teleportation serves as an excellent example of a countermeasure that allows problematic spells to continue working, while adding interesting complications that makes using them risky. If Anticipate Teleportation can be made permanent, then it adds a perfect solution to the game. Teleport Redirect, on the other hand, counters Teleport with an easily lethal trap. As a DM, I want to avoid killing an entire party due to an unwise teleport.

Players don’t like having the DM nullify the cool things they can do, even if it’s cloaked in the guise of the villain’s wards and traps. If your villain happens to use some of the gotcha effects, you’re really going to see some angry glares across the table. “So you’re saying that after you heard us talking about teleporting, the bad guy just ‘happened’ to have Teleport Redirect in place.”

Players hate when you use your DM’s knowledge of their plans to invalidate their cleverness or cool toys. (And unless you can point to the gotcha, spelled out in advance, in ink, players will always suspect this.)

The ideal defenses to game-ruining spells make the spells riskier to use without invalidating them, like Anticipate Teleport. The counter effects cannot be so devastating that players feel punished for daring to use their hard-earned magic against the DM’s pet villains. And some countermeasures, like metal sheeting, need to be within reach of canny villains who cannot afford to keep archmages on retainer.

Next: Designing for spells that spoil adventures