Part I: Two Problems and Four Solutions
With the advent of 4th edition, the philosophy of trap design experienced a number of changes. One change that breaks with previous editions of the game is the notion that the typical trap encounter includes a mixture of both traps and monsters. Previous editions of the game viewed traps as mostly occupying a place outside of combat, as dangerous elements to be placed on doors and treasure chests, not as a supplement to monsters. I love this philosophy in theory as it makes traps into exciting challenges and not random annoyances. In practice however, there are a number of difficulties with traps that often stop them from fulfilling their potential. In this article, I discuss the two problems that I feel most limit the effectiveness of traps, and discuss four possible solutions.
The Problem of Perception and the One-Shot Problem
Suppose a player proposed a new daily power that on a successful hit reduces a monster to 0 hit points. Most DMs would immediately cry foul and disallow such an obviously broken ability to function even once per day. However, many traps suffer from a nearly identical problem, namely, that of being rendered completely ineffective by a single d20 roll. Any trap that relies on a character accidentally activating the trap (for example, a pit trap or tripwire), is usually rendered useless if a player rolls a perception check and locates its area of effect or trigger squares. Worse yet, passive perception often allows a player to ruin a trap without even the effort of expending a minor action to make the check. Traps are worth an entire monster worth of XP, and should require some serious effort to defeat.
Some might argue that while traps are sometimes completely foiled with no effect on the party, they are devastating when they are activated. Thus the argument goes that traps are as effective as monsters “on average”. I think this argument is false; traps do not seem to devastate a party when activated. However, even if this were true, it means that at best in any given trap encounter, one side of the DM’s screen is likely frustrated - either the DM (who saw an entire monster’s worth of the encounters XP budget go to waste), or the players (who are being curb stomped by a trap). Swingy encounters are by definition poor encounters.
Others will argue that a trap need not rely on the players to bumble into activating it; monsters that can push or slide the players can force them to trigger it. However, this argument seems flawed on a number of grounds. Players receive a save versus such tactics, so the trap is not likely to be activated in this way consistently in an encounter. In addition, the DM is free to place hazardous terrain in an encounter without it subtracting anything from the XP budget of an encounter; a trap that costs XP to place ought to add something more. Finally, unless the DM has optimized his choice of monsters well, the players are free to use the exact same tactics on the monsters making a trap a neutral element and thus not worth XP.
A closely related problem to the perception problem is that a trap, even if it is triggered accidentally by the players, ceases to be a concern once the players become aware of its presence. While such traps can often theoretically attack each round, in practice players simply avoid the area after the trap reveals itself. I call this the one-shot problem, since the trap at best receives one shot at the players. Pit traps, glyphs of warding, electrified floors, and many other traps all suffer from this problem. Both problems can be summed up by a single observation: in order to be an effective addition to the encounter, a trap must be able to threaten the players consistently over multiple rounds of combat.
Solution One: Spotted, but Not Spoiled
Not all traps suffer from these problems. For example, the “Magic Crossbow Turret” trap in the Dungeon Master’s Guide can be triggered by any monster if the players avoid the trigger plates. Once triggered, it distinguishes magically between friend and foe and fires bolts at the players each round. Likewise, the “Cave-in” trap can be randomly triggered and attacks a different square each round, making it a continuous threat while it is active. Many traps could be modified in order to possess similar qualities. Traps could be modified to allow them to attack the players directly. For example, a pit trap might be filled with a quasi-intelligent ooze that grabs the players and pulls them into the pit. A trap may instead change its area or method of attack each round, forcing the players to remain active if they wish to avoid its effects. For example, an electrified floor might randomly electrify a different set of tiles each round, making it a threat even after being initially spotted. Of all the trap solutions offered here, this one most directly addresses the hindrances to using traps in combat. The problem with this solution is that it does not work for all traps. Many highly iconic trap concepts lend themselves poorly to round after round attacks. In fact, the most iconic traps tend to be those that only attack when a hapless character stumbles across them. This sort of trap ought to still have a place within D&D, and requires other solutions.
Solution Two: Minionizing
Dungeon Master’s Guide II and Dungeon magazine have introduced several improvements in trap design. Among the most important was the introduction of minion traps. The true value of this sort of trap seems to lay in the fact that it allows traps to operate in the same manner that they operate currently, but at a reasonable XP cost. A minion trap is activated once, makes a single attack, and then ceases to be a threat to the players. In essence, a minion trap eliminates the one-shot problem by embracing it as the natural way the trap should operate. Many traps could be turned into minions with little effort and fulfill the trap’s concept better than a standard version of the trap can. In some cases, such the “False-Floor Pit Trap” in the DMG, the trap could probably be used as is and simply awarded one-quarter of the XP listed. In other cases, the damage may need to be reduced or the number of successes needed to disarm the trap reduced to one. In addition, savvy readers may notice that this solution does not do anything to remedy the perception problem (four minion traps are as easily foiled by perception as one standard trap). This brings us to the third solution…
Solution Three: Active-only Perception
Bordering on a house-rule, this suggestion is simple: some traps may only be spotted with active perception checks. In cases where there are multiple traps or multiple trigger squares, each active perception check reveals only the nearest trigger that remains hidden to the character. In many cases, the players may not begin searching for traps until one has already been activated and it may take several rounds until all of a trap’s triggers are discovered. This allows a trap to remain a danger for most of a combat. A note of caution: it is likely best to tell your players up front that such a rule is in play, or players will likely feel cheated when the elven ranger with “skill focus: perception” fails to notice the poison dart trap. In addition, if a character’s passive perception is higher than the DC to spot a trap, consider giving the player a small clue that there may be traps in the area. This may help to reassure players that they will have a chance to spot a trap before it attacks them and prevents the game from slowing to a crawl as players minesweep the dungeon one 5-foot square at a time.
Solution Four: Front-loaded Traps
As mentioned above, minion traps often work well because they unload their entire effectiveness in a single round. Unfortunately, if one were to attempt to do the same with a standard trap (four times as powerful as a minion trap), the results would be a trap that dealt so much damage that triggering it would result in instant unconsciousness or death. Not fun for the players! However, consider a trap that delivers a powerful effect that lasts for several rounds. Such a trap is effective yet does not instantly destroy a player when activated. I call this a front-loaded trap. It answers the one-shot problem in the same way minion traps do: by only needing to be activated once. However, since a front-loaded trap represents an entire monster rather than ¼ of a monster, it needs to dole out damage and effects over time rather than all at once to not be overwhelming. Typically such a trap would have an encounter power that it uses the first time it is activated, and a weaker at-will power that it uses if activated thereafter. For example, opening a rune-covered box summons a swarm of abyssal hornets that swarm the character wherever it goes, dealing ongoing damage each round (no save). Three successful Arcana checks banish the swarm. If the trap is activated again, the swarm is weaker and merely stings the character for a round and dissipates.
The perception problem and the one-shot problem cause many traps to fail to properly challenge players, but with the solutions listed, traps can be created that are exciting, dangerous, and fun for both players and DM (well…maybe slightly more for the DM). However, the perception problem and the one-shot problem are not the only difficulties a DM may face in adding traps to an encounter. Many traps, attacking without intelligence, are as deadly to the enemy as they are to the players. If a trap is to be added to a monster encounter, a trap must be able to distinguish friend from foe. In part two of Trap Sense, I discuss ways to modify traps to make them monster friendly while remaining deadly to the players.
Until then, keep the rogue happy and the 10-foot pole handy!