Challenge Crawls

When 4th edition D&D came out they introduced a concept called a Skill Challenge. It was an attempt to give non-combat skills a game structure something like combat. Part 5 and Part 6 of the reviews of 4th edition at The Alexandrian lay out the core of why that mechanism was a failure.

I tried to find a way to adjust the mechanics to make skill challenges work but failed. It seems the core concept just doesn’t go where we might want them to go.

Recently I have looked at systems for non-combat challenges, such as looking for clues in a newspaper in Call of Cthulhu, jumping a starship between star systems in Traveller, or the various social challenges like bribery and persuasion. Those, combined with the intent behind 4th Edition Skill Challenges, has finally lead me to a generic game structure that sits between combat mechanisms and crawl mechanisms (space, hex, dungeon, urban), and from which several other game structures could possibly hang.

The Challenge Crawl.

A Brief Summary of The Core Challenge Crawl

The players state a goal, and negotiate with the GM to declare three to six steps of challenges they need to overcome to get to the goal. This will be a simple linear path. The players should try to detail the most direct sequence of steps and push as much colour into the challenges as they can. If they are inspired to note alternate paths then make a note and leave it at that. The GM then assigns a general difficulty level that will be a default for skill checks during the crawl.

Play progresses in action rounds, where the group tries to overcome the challenge at the current step by whatever mechanisms are available to them. If successful they move a step forward, otherwise they stay where they are. Repeat until the goal is achieved. Simple.

Well, simple if it wasn’t for…

Succeeding or failing at each step can have consequences, harm or benefits to characters, or easing or raising the difficulty of future steps. Some steps in the crawl may allow progress even on a failure, or may divert the characters onto a different path. The characters never go backwards. If things go pear shaped then that effects consequences, challenge difficulty and timing. Perhaps the path becomes blocked, or the group is detoured.

Characters may also investigate to find other paths to the objective, or they may find small local challenge crawls to achieve a sub goal at the current step. Characters may move onto alternate paths that are accessible from their current location in the challenge (location being a very abstract term here). Further more, characters may split up to work their way through the challenge on parallel paths, and some challenge steps may need to be overcome together as a collection of challenges before anyone can progress to the following step (for example securing both sides of a bridge before moving on to laying out the central span).

Each round of the challenge is a simple tick in the challenge clock, which may summon various changes or even block some paths. All characters experience an action round together, even if split over multiple path steps.
Play may break out into combat, possibly just as an interruption, or with the clock still ticking. Players could abandon the challenge, or they could even switch objectives mid challenge and start heading off on a new one.

This structure does not introduce anything new to play, any more than hex crawls introduce anything new to overland travel, it just provides a regulatory structure that gives players some neat mechanics for answering “what do we do next?”. It has a default action, try to overcome the current challenge and move forward. It has a default goal of “get to the challenge objective”. It is strongly player driven. It gives the game master ways to attach timed events, to throw in complications, and to change challenge levels in response to player success or failure.

Its intended to be a lightweight crawlspace that usually just arises during play, evolves as players advance, and is then thrown away when finished. Some recurring challenge types might be turned into a template by the experienced GM, but they should always allow players to get inventive and bend, spindle or mutilate their template as they work a challenge crawl.

Saving Kids from a Burning Building, an Example

This is a D&D 5e example. The characters are a fighter, a rogue, a cleric and a wizard. They have learned there are four children in the top floor of a 2 storey building that is on fire. The DM lays out an initial path while discussing with the players.

Path_Fire_initialThe DM suggests that each failure to advance will result in flame and smoke damage, initially d6 hp but increasing every 3 clock ticks. Also every 3 ticks a child may die.
The rogue does a perception check for a quick way to get in to the top floor, instead of via the stairs. The DC is 15 by default for the challenge so she rolls and gets a 16 after adding perception and proficiency. There is an easy to access window on the second floor. The DM adds the new path steps.


The rogue decides to lead the way up through the window with the cleric and wizard (Group athletics check). The fighter decides he is too heavy and encumbered for that and kicks down the door (Strength check). Both groups succeed their initial challenge step. So the rogue, cleric and wizard are in the enter window step and the fighter is on the original path at the stairs step.

The upstairs trio enter the window while being surrounded by outpouring smoke ,and the fighter decides to douse himself with water before tackling the stairs, so a quick perception check to find a pump and receptacle for the water (a new side step). Again both groups succeed. There is only one tick left before the fire intensifies however.

The upstairs trio try to dash through the room using a combination of perception check and dexterity saves and fail. They flounder in the smoke filled room and inhale smoke. They make constitution saves and the wizard and cleric take the most damage and begin coughing and spluttering. Meantime the fighter tackles the stairs, making an athletics check with the water dowsing giving him advantage against the smoke and flames. Tick 3 passes and the kids make a failed save. One of them is trapped in a burning cupboard and dies! The fire intensifies to 2d6 damage.

Both groups succeed on the next round and meet up on the top floor to start searching, making perception checks. Two pass, the rogue and fighter fail and make constitution saves. The rogue takes a lot of damage. The others have found two of the children in the nursery. Tick 5 has passed.

The fighter and rogue take a child each to the window, making athletics checks, while the cleric and wizard search for the last child and succeed. Tick 6. The fire intensifies and the kids make their saving throw with advantage from a spell by the cleric to clear the air around them.

The first two children are lowered to the ground, accompanied by the rogue. A use of athletics (strength). The others accompany the last child through the smoke and the cleric fails a step, taking another 12 damage from heat and smoke. The wizard uses a spell to clear the air in a tunnel to the window and they run to it, where the fighter helps lower them all down, and then himself while taking some more fire damage on the way down.

They have saved three of the children and not lost any characters at the completion of the challenge.

Lets now look at the formal pieces of the Challenge Crawl Structure.


Each challenge round is one tick of the challenge clock. All steps use the same abstract time unit of a tick for each challenge round. All characters involved in the challenge participate in the time passage of each round regardless of where they are in the challenge.

The challenge may have scheduled changes based on time (fire intensifies, enemy gets closer, the character to negotiate with gets bored, a door will close and lock automatically, a volcanic vent activates on certain ticks). Some time effects may be triggered by a pass or fail on a step and will then count down relative to the tick when the countdown was triggered.

A tick is an abstract chunk of time that allows the time it takes to do a skill check to be the unit of time, but should often roughly equate to a combat round time unit. If characters get involved in a combat then combat rounds and challenge rounds occur in parallel. So imagine one character is trying to pick a lock while the other characters combat guards. One combat round and one challenge tick would occur in lockstep, keeping all characters in the same time frame. If the lock is picked successfully then the characters should get to move as a group to the next step if they can disengage from the combat. The enemy might be able to pursue. Just keep it loose and don’t let the combat drown the challenge unless the players are forced to abandon it. If that happens then they may start a new challenge after the combat is over.

However some path steps may not sensibly equate to a combat round. If no combat or similar action is occurring then that does not matter. Skill ticks can just generalise as being the same. If detailed encounter time is being carried out then some skill steps may be declared as taking multiple combat rounds. Do that as rarely as possible.

The Goal

Set the challenge goal. When the last challenge on the path is overcome then the goal has been reached. You might add time constraints that make getting here harder, the time triggers may raise challenge levels or even indicate failure if the characters take too long. Its possible to have levels of success based on time or number of characters making it to the goal. Just be brief. Remember extras can be added as the challenge crawl rolls out.

Some Example Goals

These examples are drawn from actual play tests.
1 Rescue from the Burning building – time effects – fire intensifies, kids may die.
2 Assassinate the King – time effects – before the feast has finished in 8 ticks of challenge.
3 Hack Through the Blight – each failure may alert the giant spiders or make them more sensitive.
4 Convince the CEO to Give Aid to a Project – the longer it takes the less receptive she is.
5 Build a Dug Out Canoe – time effect – the river is rising every 4 ticks and the enemy are closing in, arriving in 10 ticks.
6 Smuggle an Arms Shipment Between Worlds – a string of sub challenges

The Challenge Path

The challenge path should be a linear sequence of three to six steps. Each step on the path should be a single challenge to be overcome, “pass by the guards”, “break down the door”, “make a good first impression”. The game master negotiates this out with the players briefly.

The GM then determines a default challenge level. The challenge level should be sensible for the skill mechanics of the game being played. A common challenge level is about 75% difficulty threshold, 15+ in a D20 game, or 9+ in a 2D6 game, before skills, special abilities and other resources are applied. Where the situation is dire and the characters are under stress the default could be higher. Note (briefly) alternative paths that the players bring up during the initial layout phase. Make use of them if appropriate later.
Its usually a good idea to set a maximum action time. If the time runs out then the current approach to the goal has hit a time based snag of some sort. Generally aim for maximum ticks equal to double the number of steps. That should make things a bit tense.

The Challenge Round

Each round is a tick in the challenge clock. You may or may not have time effects but keep the characters in step, even when split up. All characters and creatures are moving through challenge time at the same rate. If some initiative system is useful then use it. Do the following three phases in order to complete a challenge round. All characters involved get a chance to participate in each phase.

1) Path Phase : each character may try to detect alternate paths, or define a sub goal path. Each character may also change paths if it is possible. The general rule, slightly meta-game, is that a new path should either be one step longer than the path steps being bypassed, and a bit easier in challenge level for the new steps, or it is a step less than the steps being bypassed but somewhat harder challenge level for those steps.

2) Overcome Phase: characters try to overcome the challenge of this step. Success and failure effects are determined and applied, and characters may move on to the next step, be held back, or forced onto a new path. This is the point at which characters could end up engaging in combat. Characters each get an action, so they could do things to assist rather than specifically overcome, or perhaps ready an action to deal with some anticipated consequence of failure as with a combat readied action.
This is where the mechanics of the game are important, and is also the realm of GM rulings for handling group efforts, consequences, degrees of success and so on.

3) Time Phase: The challenge clock rolls on one tick. Time effects may be enacted. Then move to the next challenge round.

The Path Phase

Characters may each look to identify new paths to the goal from the current step, characters may instead assist other characters in their search. They may also move to the start of alternate paths that are “accessible” from where they currently are in the challenge.

The players begin by suggesting new paths that bypass one or more steps ahead of them. Finding those paths may require a skill test but that doesn’t count as an action for the overcome phase. Each character can participate in only one path check per challenge round. If the path isn’t found they can try again in another round, or the GM may declare that the suggested path cannot be found from this step in the challenge.

The players could also search for “an alternative path” as a generic action (which should be a harder check than looking for a particular alternate path) and the game master can provide that alternative (just make one up) if they succeed, provide a hint of an alternative if they fail or may declare that there seems to be no alternate path available from this location in the challenge.

The Overcome Phase

The central feature of a challenge step is an obstacle that must be overcome for characters to move forward. The obstacle should be something that could be solved with a simple skill check, although the characters could approach dealing with the obstacle in other ways, such as casting a spell. The skill system is applied as normal for the game you are playing, using the challenge rating for the current step. Any normal system for group checks, advantage, disadvantage and so on can apply. If your game mechanics allows outcome ranges that should work just fine here.

There are three basic types of obstacle for a step: Group Block, Turnstile and Pass Through.

Group Block

The most common obstacle type. The obstacle must be overcome for the entire group present to move forward, and it only has to be overcome once. For example a locked door must be opened or destroyed somehow to let every one through.


This is where the obstacle resets or remains a challenge after each success used to pass it. So characters may roll independently to get through, with some succeeding and others failing. For example a leap across a chasm where each character must try to get across the chasm themselves, making whatever skill check is relevant. Each other character may help if feasible. It may be they can only help after moving through the turnstile, for example climbing to the top of a wall and then reaching back down to help others up.

Pass Through

A pass through obstacle only allows one attempt to deal with it, then no matter weather pass or fail, the characters move on to the next step. Usually a failure will create difficult conditions for the characters in future steps. For example climbing through a passage with large spider webs slung across it. On a failure the players have twanged one of the strands, alerting the spider, but they still move on to the next step. Or a failure can harm the players passing through. Alternately success can be the thing that causes change by making future events easier or giving characters some other improvement.

Prerequisite Steps

A step may require more than one predecessor to have completed before it can be overcome. For example a step to complete the central span of a bridge requires the two steps for building the footings, one on each bank, to be completed first. Players could take on these prerequisite steps in parallel (making things faster but dividing the group) or in a sequence of their choosing.

Split Goals

In some rare circumstances there may be two or more goals with the path branching to get to each. The characters will need to decide which goal to pursue or to split up and pursue separate goals.

AvalancheCCFor example the group suddenly finds itself in the path of a landslide. There is a split goal: 1) run back, requiring two steps trying to stay out of the slide flow or remain standing and moving; 2) run forward with the first step as clearing the central flow and two steps trying to stay out of the slide flow or remain standing and moving. Its possible that the party may get split by the landslide which also leaves a dangerous obstacle to try and cross after it stops rolling.

Special Actions and Outcome Effects

Some characters may take an action that helps other characters to succeed on the current step but cause the acting character to stay behind. For example distracting a guard in conversation while other characters sneak past. This would not be feasible in a Pass Through step but would work for steps that are either Group Block (once the others are through it now becomes much harder or impossible for the next person to get through) or Turnstile (the other characters are assisted, the last character may have assistance from those already through).

Various effects can be attached to failure and success. Each failure on a step could raise the challenge level of the current step or future steps and successes could make future steps easier depending on how many failures occurred first. These steps could change depending on how many ticks have passed in the challenge. For example trying to get a favour from an NPC could result in generous aid if no failures occurred in previous steps, reasonable aid if one failure occurred, and no aid if two failures have occurred.

Failures and successes could also trigger new tick countdowns before something happens. For example a failure to bypass the silent alarm means active armed guards will show up in two ticks.

The Time Phase

Steps may have their own time tick effects – relative to when characters enter them.
Other time events may be from the start of the crawl, or start ticking from steps being entered or certain failure or success conditions.
When a countdown ends then some change is triggered. A difficulty goes up or down, paths open or close, characters may be acted against or provided with benefits and so on.


This is a quite light weight formalisation of something that good GMs probably do ( less formally ) anyway. It is intended that challenges are created on the fly, conditions and effects added as play progresses through the challenge, new paths added and characters possibly splitting up and regrouping, with combats or tactical situations sometimes breaking out and running in parallel.

There are all sorts of specific structures that could replace the use of this mechanism, which is intended for use when no other such structure exists. For example this interrogation game structure is sufficient to itself and so there is no need for a challenge crawl here if you are using the interrogation structure.

The Challenge Crawl system has been play tested artificially with other GMs five times, and “in the field” during actual games six times. In each case the players have been made aware of the structure and have made use of it. I’m not sure if this works as a hidden structure but perhaps it is useful enough as an organising framework to be of some use that way. One of its big advantages though is adventure group focus. More play seems to happen with a bit less dithering once a goal has been defined.


1) Define a goal
2) Lay out 3 to 6 linear steps – each step is a group blocker, turnstile or pass through
3) Note time effects and trigger effects that occur (be quick rather than thorough)
4) Run each challenge round

1. path phase – find alternate paths, move characters between paths. As with the main path note time effects and resolution effects for the new path steps.
2. overcome phase – characters attempt to overcome the obstacle on their current step, note outcome effects and characters moving forward, being held back or being forced to another path. As new effects occur to you note them for future steps.
3. time phase – move the clock, fire up timed changes.

3 thoughts on “Challenge Crawls

  1. This is great! Has prompted a lot of thinking from me.

    A couple of questions/thoughts, if you don’t mind:

    How would you handle a chase? Rather than a set number of steps, it feels like the number of steps should increase by one for each passing round.

    An alternative for turnstiles could be that once more than half the PCs succeed, all PCs succeed at that step (inspired by the group check rules). Would stop anyone from getting stuck for too long, while still rewarding parties with broad/overlapping skills.


    1. Chases: Each side is separated by a distance. Skill checks open or close. Two types – just get away, or get to an objective before being caught.

      Get to objective, there is a total distance clock. Some choices slow the move forward or increase the total distance. Choices involve throwing obstacles into the path, but harder to move ahead, Ducking through a longer route that is easier to open distance on, but takes longer to get to a destination. Chaser trying to identify destination may have harder time catching up. Known destination chaser may attempt to head off but failure risks losing distance, or even losing sight of the target.

      It starts with a linear path with landmarks or distance to destination marks.

      Just opening distance involves lots of branches, head for the woods, further away but easier to lose the chaser, jump on the boat and row off out of reach if you can get there first but its a hard, uneven surface between here and there, run into the crowded market and dodge about the people, hope the chaser gets held back by obstacles, but run the risk of dead ending.

      In the end its always about what is interesting about a chase? Its the incidents and choices and the tension as a goal becomes closer or further away.

      Regards turnstiles, where appropriate the more people that made it and that can help the more likely it is the others will then make it. (The D&D 5e rules about helping are not so good here, in that 2 people helping to lift a friend up is better than one, but the help rules don’t allow multiple helpers).


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