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Caltrop Core SRD

Designed by Lex Kim Bobrow, Caltrop Core is a game system built on a handful of D4 dice.

The game mechanics fit on a single page.

When you consider the community uptake, the system has been a huge hit. There have been more than 110 games designed using Caltrop Core. The first-ever Caltrop Jam has 92 submissions.

Primary Mechanic

  • D4 dice are used
  • Characters have a stat value
  • The number of D4 dice rolled are the same as the stat
  • At least one of the dice has to get a target value or higher to succeed (normally a 4)
  • More dice = better chances of getting the value

How does it work?

With only 4 possible values on a D4 dice, the results are easy to remember.

1 – Absolute failure. (You don’t get what you want and things get a lot worse)

2 – Partial failure. (You don’t get what you want)

3 – Partial success. (You get what you want, but things get complicated)

4 – Absolute success. (You get what you want, and more)

Is that everything?

Yes and No!

Rolling a simple D4 is the core of the Caltrop Core system. However, the system really shines when you roll more than one dice.

The SRD talks about using “stats” or “tokens”.

Using Stats

If you have ever played D&D, you will have used stats to influence the outcome of various rolls.

When you use the Caltrop Core system, you want to assign stat values of 1 to 3.

When the stat comes into play, pick up and roll that number of D4 dice. For example, if you have a stat value of 3, roll 3 dice and take the highest value.

The more dice you roll, the greater the chance of achieving success.

Using Tokens

In a token based game, players can gain and expend tokens. The more tokens you spend, the more dice you can roll.

Once again, you take the highest roll.

Situational adjustments

There may be situations where you need to adjust the odds slightly before rolling.

For example, if you are climbing a wall, you might use the dexterity stat.

But if it is raining, you might take one of the D4’s away. If it is really pouring, you might take away 2 d4’s instead.

This is up to the game designer, but worth considering. (Thank you cubist137 from for the suggestions)

What about combat?

The same table can be mapped to combat rolls.

Pick up and roll the appropriate number of dice. For example, If your strength is 2, you may pick up and roll 2 dice, and take the highest value.

Lets have a look at how the Caltrop table can be applied to combat

1 – Absolute failure. (You take 2 damage as the opponent counters your attack)

2 – Partial failure. (You do not hit and are in the same position as before)

3 – Partial success. (You deal and take 1 damage)

4 – Absolute success. (You deal 2 damage)

Of course the tables can be modified to suit your particular game.

The Caltrop Core SRD goes into a lot more detail, and has examples of how the system can be used in different situation.

What makes it different

Everything is decided by a handful of D4 dice.

The community loves it, and there are plenty of games already available.

My thoughts

This is the core of a very robust gaming system.

The system is incredibly simple to understand and solid in its execution.

I can’t wait to see some of the games that come out.

I am especially interested to see how designers expand on the concept or introduce their own twists on things.



The Caltrop Core SRD is licensed for use under a Creative Commons Attribution-ShareAlike 4.0 International License.

Where can I get it

Caltrop Core was designed by Lex Kim Bobrow @titanomachyRPG

SRD Web:

Link to 110+ games using Caltrop Core: