D12 Tension System
The D12 Tension System is a way of making the world feel more dynamic, both for group and solo play. The idea is simple: the current "tension" (which is a value from 1 to 10) in the campaign is kept track of at all times, and will have various effects. With increased tension comes increased danger. Some events will increase the tension, while it mostly only decreases when the PCs accomplish something which resolves a problem or situation.
The purpose of the D12 Tension system
The idea is to have the PCs' actions, and other events in the world, have mechanical effects. The level of danger should rise and fall dynamically as events unfold. The system is designed to encourage players to consider the results of their actions, and to give a meaningful benefit (of decreased danger) to solving problems and completing quests.
What Tension can influence
The D12 Tension system primarily has two mechanical uses:
- Tension can influence the risk of something dangerous happening (random encounter, cave in, alarm going off) by using Tension rolls.
- Tension can influence the severity of a roll result (how dangerous are the enemies, etc) on a Random table with Tension.
Tension rolls
Tension rolls are used to determine if something dangerous or risky happens.
- Formulate a yes/no question where the "yes" answer is the dangerous one, such as "Is there a random encounter", "Is the next dungeon room guarded by enemies?", or "Does the building collapse?".
- Roll 1d12.
- If the result is less than or equal to the current Tension value, then the answer is yes - there is a random encounter, the next room is guarded, or the building collapses, and so on.
Bear in mind that in most games, Tension rolls should probably not be used to determine things about characters, such as "does the guard spot the PC sneaking by?" or "Does the PC fall into the pit trap?", because most games have other mechanics to resolve that, such as Perception rolls and Dexterity saves.
Designer's note: The fact that a D12 is used for this means that even if the Tension value is at its maximum of 10, there is still a small chance that the roll will yield a safe result. Incidentally, this D12 is also what gives the system its name.
Random tables with Tension
A Random table with Tension is a table with results in the 2 - 20 range. To use it, you simply roll 1d10 and add the Tension value to get the result. The results in the table should be roughly sorted by danger, with the safest ones near the top and the most dangerous ones at the bottom. This way, you will only get the most dangerous results with a high Tension value - which is the point.
A quick example - Random city events with Tension
| 1d10+Tension | Event |
|---|---|
| 1 | There is a public celebration nearby |
| 2 | Children play loudly in the street |
| 3 | A religious procession passes by |
| 4 | A public debate is taking place |
| 5 | An authority figure makes a loud proclamation |
| 6 | A parade blocks the street, causing irritation |
| 7 | Someone is robbed |
| 8 | Someone is being stalked |
| 9 | There is a loud argument in the street |
| 10 | Someone is trying to run from something |
| 11 | The City Guard have arrested someone |
| 12 | Someone approaches asking for help |
| 13 | Someone approaches, offering something |
| 14 | Someone falls ill or is injured in the street |
| 15 | Guards are trying to control a volatile situation |
| 16 | A fight breaks out |
| 17 | Two factions are publicly clashing |
| 18 | An innocent bystander is attacked |
| 19 | A fire breaks out |
| 20 | A riot breaks out |
Using such a table without the D12 Tension system
Random tables with Tension can be used without the D12 Tension by simply replacing the 1d10+Tension roll with a 1d20 instead. This means that all types of events (safe and dangerous) can happen at any time. Eagle-eyed readers will also have spotted that the "1" result in the example table above can only happen when rolling 1d20 instead of 1d10+Tension, since the Tension value will always be at least 1.
Designing Random tables with Tension
Since such tables need to support roll results from 1 (or 2) to 20, it may seem daunting to come up with tables that have so many results. But you don't have to - you can group the results into ranges. Let's have a look at an example:
| 1d10+Tension | Result |
|---|---|
| 1-4 | The enemy faction remains passive |
| 5-8 | The enemy faction sounds out a scout |
| 9-12 | The enemy faction launches a patrol |
| 13-16 | The enemy faction mounts a raid |
| 17-20 | The enemy faction makes a full assault |
Since we've grouped the results into ranges of 4 each, we only need 5 entries on the table making it easier to create than a full 20-entry table. But the Tension value still has the desired effect.
Okay, but when does Tension change?
When Tension increases is largely up to the GM. When the GM feels that it's appropriate, then they can increase Tension by 1 or a few points. Examples could include:
- Tension could be increased by 1 point when two opposing factions have a public disagreement in a city, which makes the citizens uneasy which in turn can affect the risk of unrest.
- Tension could be increased by 2 points when the party loudly breaks down a door in a dungeon (as opposed to silently picking the lock), thus increasing the risk for wandering monsters who may have heard the commotion.
- Similarly, tension could be increased by 3 points when combat breaks out in an enclosed space.
Tension should only decrease when the PCs (or, theoretically, someone else) accomplishes something to decrease the tension of a situation. This motivates the players to try to deal with issues and solve problems rather than just laying low.
- If the PCs find and apprehend a murderer in a city, Tension could decrease by 1 point since the citizens now rest a bit easier at night.
- When the PCs find the missing child, the Tension in the village could decrease by 2 points as the villagers are now less worried that more children will also go missing.
- If the PCs repel a raid against a settlement, Tension could decrease by 3 since the inhabitants now feel a lot safer.
Okay, so what should the starting Tension value be?
That's up to the GM. If play starts in a relatively safe and peaceful settlement, it should start at 1 (remember, 1 is the lowest allowed number here, not 0). But if the starting point is in the middle of an active battlefield, it should probably be 10 or close to it.
Should there be multiple Tension values or just one?
In a lot of cases it will make sense to have different Tension values. For example, in a city-based campaign the city as a whole could have a Tension value reflecting the current situation within the city walls. But if the party ventures into a dungeon, then that dungeon should have its own Tension value, probably starting at 1 and increasing / decreasing with the PCs' actions.
Is this a player-facing system?
In other words - should the players be aware that you as a GM are using this system?
Well, that's up to you and your group. Some groups like having mechanics like this exposed to them. "Holy shit, Tension is up to eight now? Come on, we have to wrap this dungeon up quickly before we get overrun!"
Other groups might feel that such mechanics, when exposed to them, is "too boardgamey", and would prefer if the GM instead says things like "Are you sure you want to break down the door? The noise may attract enemy attention. It's your call." But even in such cases, it may be beneficial if the players know that there are mechanics behind the GM screen which will affect them, and that their actions will have mechanical consequences, even if they don't know the specifics.
If you're not sure what your group prefers, just ask them.
The Tension value can be used for many things
The Tension value can be used in many different ways. Besides the examples given above, here are some additional ideas:
- The D12 Dungeon Crawl System is based on the D12 Tension system.
- When the enemy gets reinforcements in combat, the number of enemy soldiers arriving could equal the Tension value, or half the Tension value, and so on.
- The Tension value, perhaps divided by 3, can be used to affect Reaction rolls in an appropriate direction. A neighboring allied city may be less likely to send reinforcements if their Tension value is high, but the Town Guards may be more likely to accept your help if the Tension value in town is high (read: if the proverbial shit has hit the fan), and they think that they need all the help they can get.
- As Tension goes up, so could the local prices of goods.
- In a settlement, the Tension level could affect which shops and services are still open for business. If Tension is allowed to rise too high, the city gates might be closed and the city goes into lockdown, either locking the PCs in or out.
I'm sure you can come up with additional uses too.