Assigning difficulty checks (DCs) for skill challenges can be a frustrating experience. Some checks have set DCs that are provided for the DM. Examples of this are traps and locks that have a predetermined level of difficulty. A skill check that doesn’t have such an obvious DC is Stealth for sneaking past a guard. Why is this check less obvious? Because it’s opposed by the guards passive Perception. The tougher the guard, the higher his Perception.
This raises some mechanical questions that DMs needs to answer. First, is it necessary to create a guard for the skill challenge? If it’s needed, what level should the guard be? If the PCs are in the paragon tier should the guard also be paragon? Does that even make sense? If the PCs fail the check and the guard notices the PC, what is the guard’s response? Will he attack, call for backup or runaway? Suddenly, we have a lot of extra contingencies that need to be planned for but we haven’t answered the original question. What is the guards passive Perception and just how difficult is it to sneak past him?
I am of the opinion that the less mechanics required the better. In other words, don’t role up a city guard for this encounter. Fortunately, the DMG provides set DCs that scale based on the characters level. Of course this also raises an additional question. Depending on the level of the PCs is this skill check even necessary?
Let me explain. At first level, a skill challenge where the party sneaks past the guard is tense and filled with drama. The guard is every bit as tough, perhaps tougher, than the PCs. This continues to be true throughout the heroic tier. However, once the PCs hit paragon and beyond sneaking past a common guard looses its luster. The drama and excitement of this type of challenge is gone. The party has been there done that. So before you go and determine the required DC ask yourself if the check or the skill challenge is even necessary.
Now, assuming that the skill check or challenge is required and that this event is intended to be an intense moment full of drama and action, a DC for the check is required. If you have no intention of having the PCs fight the guard, then you have no reason to create a NPC for this situation. What you need to do is decide on what a reasonable DC would be for the situation. This requires that you ask some questions about the guard.
How switched on is the guard? How well does he know his patrol route? Was he drinking before his shift? All of these questions are role-playing questions that the DM can decide. If the guard is switched on and a capable veteran it’s a hard check. If he’s a new recruit who is fairly nervous things won’t be so difficult for the PC.
Adding some role-playing flavour into this scenario will make it more enjoyable for your PCs. If they realize that the guard is older and wears his armour with ease, the PCs might surmise that this is guard is a veteran. Similarly if the guard is constantly fussing with the straps and buckles on his armour the PCs might be led to believe he is a new recruit.
How do the PCs determine the guard’s alertness level? Perception checks, of course. Which is another variable while putting together DCs for this skill challenge. Usually the higher the PC rolls the more information they can learn.
Of course the DM should also know why the door is being guarded. Designing a 10 x 10 room with a guard in it is not wise encounter design and neither is placing a guard in front of a door just because you want the PCs to sneak past. The encounter and therefore this skill check requires meaning. If that can’t be provided then it should be removed. If the PCs are level 15 and this is a town guard of a settlement with less than 10,000 people, why is the check required? It’s unlikely the guards would even notice the Fighter in plate armour sneaking past. The Fighter after all has had a few levels to practice being sneaky.
Is the check required because of the larger story of the campaign? Is the guard covering for a rookie who is off tonight attending a wedding? Perhaps the guards have been attacked by unknown forces recently, requiring them to be extra vigilant. The reason matters because it’s tied to the story. This makes it important to your players, so give the rational behind the check the consideration it deserves.
The real question the DM has to ask himself when designing the challenge is how difficult do I want to make this skill challenge? If the answer is very difficult, then make the DCs hard. This type of thinking takes the thinking right out of the equation. The important distinction is to know why the check is required in the first place. Now all you need to do is create the narrative that will drive the skill challenge forward. In other words, what happens after the PC sneaks past the guard?