Hazard System v0.2

The Hazard System is the gameplay engine behind The Final Castle. Though it assumes games of fantasy adventure and exploration, it is modular and should be easily adaptable to many kinds of tabletop RPGs. I use some variation on this approach for pretty much every game I run now and I don’t think I could go back to any other method of pacing or timekeeping. It is the natural outgrowth and generalization of the overloaded encounter die.

Gameplay proceeds in turns at different fictional timescales with each turn accompanied by the chance of a hazard. What “hazard” means will vary based on the context. For example, a hazard during a haven turn, when characters are recovering between adventures, might be a natural disaster, while a hazard during a dungeon turn, a much shorter period of fictional time, might be an encounter with a wandering monster. The hazard system also serves as a general timekeeping and resource tracker.

The text below the divider is released under a Creative Commons Attribution 3.0 Unported license. Attribution:

Necropraxis Productions Hazard System v0.2 http://www.necropraxis.com/hazard-system/

A PDF is also available.

Currently, several references to undefined terminology from The Final Castle remain, such as Ability Tests. It should be relatively easy to interpret these in light of whatever system you are using, but the final Hazard System text will likely be entirely system agnostic. Additional turn types will also likely be included (Domain Turns and Generation Turns, particularly).

Hazard System v0.2

The game proceeds in turns of several different types. The turn types are haven, wilderness, dungeon, and combat. Each represent a progressively smaller amount of fictional time within the game world, though the exact durations are usually abstract. The passage of time within each turn is a resource to be spent wisely, as the hazard die is rolled for every turn that passes to represent potential danger.

The Hazard Die

The six-sided Hazard Die deploys threats, manages resources, keeps time, and tracks light. In short, it is the engine that drives gameplay forward and the heart of the Hazard System. Every significant action, whether in town recovering, traveling through the wilderness, or searching a dungeon corridor for traps, takes a turn. Every turn is accompanied by a roll of the Hazard Die. The exact interpretation of the die result varies by turn type, but the outcomes are conceptually similar. A haven hazard might be a shortage of supplies while a dungeon hazard might be a wandering monster.

Players other than the referee should roll the Hazard Die to make the time cost salient. After rolling the Hazard Die, hand it to another player so that everyone gets a chance. If playing in person, rotating clockwise around the table works well.

Beginning the game

Start a new campaign with the first Wilderness or Dungeon turn of an adventure. Players should choose a clue or quest from the Tavern to pursue. Roll HP following Recovery guidelines to determine initial HP.

Starting and ending sessions

Sessions should begin and end in a Haven if possible. This allows the the players and PCs to vary between sessions. After a session, players should tell the referee if they are going to follow a different clue or Quest during the next session so that the referee can do any preparation required beforehand.

Haven turns

To recover and replenish resources in a civilized refuge, take a Haven Turn. The exact fictional duration of a Haven Turn can be anything from a few days to several weeks. It is rarely necessary to interrogate the details.

  1. Roll the Hazard Die and resolve any hazard
  2. Pay upkeep: accommodation, retainer, property, and so forth
  3. Recover (roll HP, applying accommodation modifiers)
  4. Process retainer loyalty
  5. Reckon XP gained and level up if appropriate
  6. Buy or sell items, repair damaged gear, or recruit hirelings
  7. Optionally, take one Haven Action (scribe scroll and so forth)
  8. Prepare spells
  9. Review rumors and news

Haven Hazard Die results

  1. Complication (introduce at any point during the turn)
  2. Clue about next complication
  3. Abatement of one or more (by referee whim) haven conditions

Ignore results of 4 – 6. Starred complications persist as conditions.

Haven complications
d20 Complication d20 Complication
1. Assassination 11. Insurrection *
2. PC challenged 12. Invasion *
3. Curse * 13. Jailbreak
4. Earthquake 14. Mobilization *
5. Flood 15. Monster attack
6. Falling star 16. Murderer on the loose *
7. Famine * 17. Pestilence *
8. Fire 18. PC slandered
9. PC impersonated 19. PC item stolen
10. Inflation * 20. Winter *

Wilderness turns

Wilderness turns alternate between day and night. Characters taking two non-camp wilderness actions in a row suffer 1 damage and gain a point of Exhaustion. Choose a wilderness action: travel, search, explore, hunt, track, or camp.


Move the party into an adjacent area or access a known landmark such as a haven or dungeon.

Search, Explore, Hunt, or Track

The party leader makes a Search Test to locate (and enter, if desired) a hidden feature. To Explore, Search without a stated goal. Success reveals a random hidden feature. Track is a Search to follow a quarry. Hunting yields 1d6 rations (adjust for terrain) per hunter. Night applies a -1 penalty to Search, Hunt, or Track.


Camping requires a bedroll and consuming 1 ration per character. One person may stand watch for each four party members without impairment. Ignore Hazard Die results above 3.

Wilderness Hazard Die results

  1. Encounter (may differ between day and night)
  2. Percept (regarding next encounter)
  3. Locality (mechanical change in environment)
  4. Percept (regarding hidden feature)
  5. Resource exhaustion
  6. Lost


Travel is no longer an option if a party is lost. Search must be used to locate a landmark before travel can be resumed.


Each point of Exhaustion imposes a cumulative -1 penalty on all physical Ability Tests. This adds to Encumbrance penalties.

Dungeon turns

Some actions that require a Dungeon Turn include climbing, forcing a door, guarding the party, listening at a door, moving to a new area, searching the current area, and other tasks of similar scope. Each player may take a different action during a Dungeon Turn. Dungeon Turns can represent a fictional amount of time anywhere between a few minutes to an hour, though most commonly are about 10 minutes long.

In practice, the passage of Dungeon Turns can be more fluid than selecting actions by name, resolving any hazard, and iterating. However, always remain cognizant of lurking dangers and call for the Hazard Die whenever significant actions are taken.

Free dungeon actions

Minor actions often do not consume a full Dungeon Turn. Interacting with particular features such as looking under a rug, opening doors that are not stuck, and pulling levers are all free actions. Clever use of free dungeon actions can forestall the Hazard Die and thus decrease risk.

Dungeon Hazard Die results

  1. Encounter
  2. Percept (regarding next encounter)
  3. Locality (mechanical change in environment)
  4. Fatigue (take 1 damage unless the next turn is spent resting)
  5. Resource exhaustion (spell duration, etc)
  6. Light source exhaustion (any or all light sources go out)

Reasonable resolution

Fatigue and light source results may be ignored when they do not make fictional sense, such as during the first few turns of an exploration. Exhausted light sources rarely all go out at exactly the same time, but instead dwindle over the course of the turn, and may be relit given sufficient PC resources.

Released under the Creative Commons Attribution 3.0 Unported license


Necropraxis Productions Hazard System v0.2 http://www.necropraxis.com/hazard-system/

12 thoughts on “Hazard System v0.2

  1. Scott Anderson

    I have worked out combat rounds down to a finite number of categories of action so that players may simultaneously declare their actions by revealing a card prior to throwing for initiative each round: skirmish, volley, cast a spell, withdrawal, other.

    I can see how turns of other time periods (exploration turn, wilderness day, “haven” session) should also have a finite number of categories of action so that declaration can be handled n the same way.

    In this way, a table with eight players (or a noisy table of fewer) can get through their game turns in a reasonable amount of real time.

    Again you have preceded me down this particular intellectual catacomb as you so often do.

    1. Brendan Post author


      Hey, sorry your comment didn’t show up right away. The spam detector had a false positive and I needed to approve it by hand.

      I’ve done a similar thing with combat too, but it still needs more play testing and is not ready for sharing yet. I ended up with more categories than you, though I suspect you get a lot of mileage out of the “other” option.

  2. Paul Schaefer

    I like this a lot. It offers a simple way to track time and resources while offering a variety of encounters and situations as opposed to just a random monster. It combines all those elements that I would like the use, but always get scattered and forgotten about during my game prep. And it to s completely hackable to any game with very little work. Great example the f what should go in an RPG toolbox.

  3. Charlie Vick

    Though the Torchbearer reference shines, this also reminds me of the ‘world engine’ concept presented in Slumbering Ursine Dunes, though that module presents more of a system by which the world slides into or out of Weird Events happening thanks to PC actions. Basically, the PCs have an impact on what kind of random encounters they’d see, and potentially cause environmental changes as well (rains of blood, wild magic, invading hordes). http://hillcantons.blogspot.com/2012/12/the-weird-is-rising-thanks-world-engine.html has some details, and probably explains things better than my overstimulated brain.

    Once you start changing the likelihood of certain random events – especially at an Overworld / region-impacting level, you’re right at having a world engine, as I understand it. Though really, just having a world that changes dynamically over time, with or without the PCs doing things, will do a lot in terms of making the place seem alive.

    This is great. Cheers!

  4. Rob Brennan

    Nice ideas. A question – if time is variable, how do you handle movement distances (exploration) under this system? eg do you roll randomly for the time between events?

    1. Brendan Post author


      I use hexes that represent 1 day of standard travel rather than absolute distances, and modify chances slightly for means of transportation, such as riding horses into the ground (but such modification show up surprisingly rarely).

      It would also work, if using something more like a point crawl, to roll once for each distance between a point or make a ruling about how many days are required (perhaps incorporating randomness as you suggest). This is, for example, how I managed the ruin crawl style play of investigating the barrows and swamps above Barrowmaze (I generally required one hazard roll to move between barrows, but had the PCs wanted to go from the bottom of the map to the top, I probably would have ruled that to be two hops rather than one).

      The most important thing, to me at least, is making the choices impartially consequential and salient.

      1. Rob Brennan

        But if using this within a dungeon say, the characters exploration rate is traditionally say 60-90 feet a turn. Random encounters occur in 1 in 6 on every 2nd turn. If you have variable length turns then sometimes a preplanned encounter/environment “should” occur before the next random encounter.
        By the way this approach very much suggests to me event-based simulations which are often used for network protocol evaluation – the basic idea is that there is no need to simulate the “in between” times where nothing is happening, just to jump from significant event to significant event. This contrasts with the normal D&D method of simulating everything on a 10 min clock (whether something interesting happens or not in that 10mins).

  5. Charles Ferguson

    I think this is brilliant. Slashing book-keeping requirements while retaining meaningful resource constraints is a personal grail of mine. Your mechanics take a giant leap down that road while tying it to the requirements of fiction: an overt nod to the metagame beneath such constraints that, because it works within the familiar (the wandering monster roll) somehow manages to largely keep the curtain intact.

    I use a “light roll” that’s broadly analogous to the light rules in your hazard engine but I never made the leap of stepping back and tying them to the wider context of hazards in general. Consequently their mechanics are fiddlier and not really satisfactory. I like yours much better.

    One thing. The last paragraph of the pdf says:

    “Fatigue and light source results may be ignored when they do not make fictional sense, such as during the first few turns of an exploration.”

    I grappled with this for my own light rules and came to the position that I would trust the dice. The dice always say what happens, the DM’s job is to explain why, in a way that makes fictional sense. If the lights go out on the first turn, they go out: bad oil in the lantern, the wick is dodgy, the torch flares and begins to sputter, a gust of wind, foul air, a puddle or slime or uneven footing means the light bearer has to roll to avoid dropping the light, and so on. Don’t know if that would work for you, but it goes fine in my games (once I got used to it).

  6. ktrey parker

    Re: Fatigue and light source results may be ignored when they do not make fictional sense, such as during the first few turns of an exploration.

    Perhaps for the first Dungeon Turn the Dungeon Hazard Die can be treated as a d3, expanding to the full range of d6 results after enough reasonable time has elapsed in the fiction? Naturally, this would still somewhat depend on the fictional length of the “Turn,” so another option would be to overload the initial Dungeon Hazard Die to represent the number of turns before the 4-6 results start materializing.

    This would produce at least one non-resource/fatigue result prior to expanding the possibilities to include the grind/drain stuff.

    I really like this procedural approach’s almost fractal nature, and will definitely be trying it out!

  7. Pingback: House Rules for upcoming D&D 5E campaign | Take On Rules

Leave a Reply