28 February 2015

Earthdawn 4E: Part 4 - Math and Reducing Complexity

This is an ongoing series about Earthdawn Fourth Edition. Introduction and Index.

Everything contained here is the work of a fan and not associated with FASA Games.

A brief warning: this is going to rapidly descend into the realm of letters as numbers, but nothing will be terribly complex. The goal is to explain how some of the changes to Earthdawn Fourth Edition (ED4) were made for the game to be more accessible to players who are not mathematically inclined. Also, by understanding the new, underlying math, there is significantly less need to use the characteristics table during character creation. Except for carrying capacity.

Fans of Earthdawn are likely familiar with the underlying math which has been a part of the system since day one. Use of the Fibonacci sequence for legend point costs creates a natural increase which scales just right. The step number is also the average result of the dice used (don't forget to account for bonus dice if doing this at home). Once multiple dice are used, they also tend to create a normalized distribution, though not all steps were created equal in this regard. Thus the monkeying with D20s and D4s in Third Edition and ED4. Even the result table roughly equates to standard deviations of results.

Towards these ends, the role math plays in the system and how it is used was a factor under significant scrutiny during the development of ED4. The first and perhaps most significant change was to the Result Level Table. It was off-putting to many existing and potential players and GMs to consult a table to determine your degree of success. This step takes just long enough that it can slow the action down. Also, you have to have the table nearby at all times. 

The applied fix was to remove result levels and instead use successes. Making the difficulty number is one success and every 5 above it is another success. The magic number 5 was selected for three primary reasons: 1) It roughly maps to the old result levels, which gives an experience with little noticeable difference, 2) manipulating multiples of 5 in your head is rather simple for everyone, and 3) it feels natural.

Moving from there, the base value provided by additional successes tends to be +2 to something. Not everything, but we wanted a standard number to use for as much as possible to reduce the amount which needs to be looked up. Instead, it is a case of remembering the exceptions - of which there are few and largely relegated to spells. Different standard numbers were playtested with 2 and 3 coming out as the best for gameplay. Ultimately 2 was selected because manipulating multiples of 2 is easier than multiples of 3.

The next table to tackle was the characteristics table. Here it was a case of identifying simple formulas which mostly align with the old results. The goal behind this was to allow people who noticed the underlying math to use derive all of the characteristics without the need to reference the table. Actual formulas weren't provided for space reasons and playtester feedback included the phrase "... and then my eyes glazed over..." more than once. Here are the underlying formulas:  

Step Values: Attribute/3 (round up) + 1 [This was not changed]
Defense Values: Attribute/2 (round up) +1
Unconsciousness Rating: Toughness * 2
Death Rating: Unconsciousness Rating + Toughness Step
Wound Threshold: Toughness/2 (round up) + 2
Recovery Tests: Toughness/6 (round up)
Mystic Armor: Willpower/5 (round down)

There are a lot of different manipulations going taking place and there is no expectation for these to be internalized out of the gate. However, GMs who can become comfortable with these will find it significantly easier to generate accurate NPCs on the fly (for Wound Threshold, treat it like a Toughness Defense +1).

Next on the list is Durability. The way this talent was written in previous editions (e.g. 7/6) was frequently a source of confusion to new players and frustration to those who were not good at math. Familiarity cures the former, but the latter is only exacerbated by taking multiple disciplines. Navigating the treacherous shoals of Durability rules with multiple disciplines if your first discipline is not Warrior (or something else with 9/7) can turn ugly.

Turning it into a function of the discipline solved many of these problems by simply providing the best value available for a given circle. It was a little complex to some players during playtest, but infinitely better than previous executions and ultimately no more difficult than taking the highest defense value of those available.

Using the death rating from durability created a second set of calculations and feedback for this was negative from newer players, particularly when getting involved with multiple disciplines. Instead of basing the boost to death rating off of Durability, it was changed to the highest circle. This is a simple value to determine regardless of the number of disciplines a character possesses and how convoluted their Durability ratings and ranks are.

Final formulas for unconsciousness and death ratings are below:

Unconsciousness Rating: Toughness * 2 + (Durability Rating * Durability Rank)
Death Rating: Unconsciousness Rating + Toughness Step + Highest Circle

Since it essentially comes out The end result is easy for the mathematically inclined to perform in their head and also reduces the complex manipulations (yes, basic multiplication is complex for some people) in favor of simple addition. This is a case where understanding the underlying math and how death rating relates to unconsciousness rating can greatly simplify operations.

The final numbers which were played with are in magic. Dispel, learning, sensing, and thread weaving difficulties were all simplified a great deal. Sensing difficulties (from spells) in particular are much easier since they are always based on the circle of the effect instead of maybe the circle or maybe the effect test from the spell. They are based on Circle and a static modifier, as seen below:

Dispel Difficulty: 10 + Circle
Learning Difficulty: 5 + Circle
Sensing Difficulty: 15 + Circle
Thread Weaving Difficulty: 4 + Circle
Reattuning on the Fly Difficulty: 9 + Circle

It is worth noting reattuning on the fly is specifically one success greater than the basic thread weaving difficulty. The static modifier for thread weaving is 4 instead of 5 based on feedback from playtesting. It was just enough of a difference for a spellcaster to be confident at any given circle of weaving the thread, with karma providing the boost to help with reattuning on the fly or reaching for an additional success on the thread weaving test.


  1. This website is an incredible resource and the details on the design are incredibly helpful for a gamemaster learning a new system.
    Thank you and keep it up!

  2. Don't hate me for being late, but I only found out about 4th Edition of Earthdawn last year. I have been working on a ruleset for Fantasy Grounds to make it easy for me to play with my group. I ran into some problems trying to figure out the carry capacity limits, but from your comment about it, I'm guessing it isn't a nice easy formula. I'm always glad to meet a mutual fan of Earthdawn and Math.

    Even if it's extremely convoluted, I would love to see what information you do have about the calculations for the carry capacity. Unless it's literally just arbitrary numbers.

    1. Greetings and welcome! New fans are always welcome and it's never too late to get started. You are correct, the formula for carrying capacity isn't nice, but here it is:

      A = Attribute Value

      Hopefully this is useful. You should check out the FASA Discord server and connect with other fans of Earthdawn. It's pretty active without being a chore to keep up with.