House Rule Review #2: Experience Points

Update 10/2/2016: Added subsections on monsters with fractional CRs, monsters whose CR is less than APL − 8, and an alternate method for awarding XP for parties with mixed character levels. Also fixed Table 1 so it includes XP values for every relative CR covered by Table 2.

This is the second in a series of posts analyzing some house rules for d20 fantasy gaming that I wrote and later abandoned. The planned scope of the series was initially four posts, then was reduced to three. Now it may prove a little more open ended, since I've found a more recent copy of the house rules in question, which is giving me more food for thought.

The first post in this series, on character creation and point-buy systems, can be found here.

All text after the first paragraph under the heading "My New Solution" is open gaming content under the terms of the OGL.

Eternally escalating experience point totals have been one of the annoyances, albeit a minor one, of D&D and its offshoots for a long time. In any game where characters could advance to 20th level or beyond, XP totals could add up into hundreds of thousands, or even millions. Of course, these numbers aren't as big a problem today, particularly for players, because every cell phone has a calculator. However, it can be an inconvenience for GMs designing encounters in PFRPG, since they have to sometimes add and compare these large values, and could have to do this for every encounter in an adventure.

My Old Solution

In my old abandoned house rules, I actually tried to make a more systematized version of an optional approach to leveling up in D&D 4e. That approach had the DM give the PCs another level after about 10 appropriately challenging encounters. Easy encounters (as defined by the DM) would count as only half an encounter, while hard ones could count as two or three. However, there were no concrete rules for how to value encounters, and I wondered if a more rigorous version of this alternate rule could be used in PFRPG.

I started with the PRD Encounter Design chart and assigned a "challenge point" or "encounter point" value to each difficulty.* An encounter with a challenge rating equal to the average party level minus one had a value of half a point, while an encounter with CR equal to the APL +3 was worth three points. This system was simple, but it didn't match the proportions of encounter math in PFRPG very well. This was another of the problems that led me to abandon the house rules.

However, another concept that sprang from this system has lived on in my d20 heartbreaker project, and it's a concept that I think is worthwhile. What if, instead of a giant table listing different XP requirements for each level, there was just one XP value for advancing to whatever the next level was, whether it was 2nd or 20th?

*I switched back and forth between these terms throughout the manuscript, and never did a thorough find/replace to settle on one.

My New Solution

Introducing Rollover XP. The version presented here is not as simple and elegant as the one in my PFRPG houserules or the one in my unfinished d20 heartbreaker, but it uses numbers and methods that are more familiar to the average Pathfinder GM.

This system uses Fast, Medium, and Slow experience tracks like the standard system given in the PRD. However, it takes a constant amount of XP to gain each new level. This amount is equal to the number of XP needed to advance from 1st to 2nd level under the standard rules: 1,300 per level for the Fast track; 2,000 for the Medium track, and 3,000 for the Slow track.

And now for the feature that gives this system its name: the rollover. Instead of keeping track of an ever increasing running total of XP earned throughout their character's career, a player only needs to keep track of the XP earned during the current level. When the character earns enough XP to advance to the next level, the XP total is set to zero + the difference between earned XP and the amount needed to advance. For example, if Althar the Ranger is playing in a Medium track campaign and has 2,050 XP, he advances to the next level (whatever level it is) and his player resets his XP total to 50.

Monster XP Values and Encounter Design

To make this system work, monster XP must be calculated differently from the standard encounter design rules. In the standard rules, a monster's XP value is a constant number based on its CR. In the Rollover XP system, that value changes based on the difference between the monster's CR and the PCs' APL. Table 1 gives the XP values for monsters based on that difference. It covers relative CRs ranging from eight below the APL to three above it and gives values for both total XP and individual XP.

Table 1: Monster XP Values

Monster CR vs. APL	Total XP	Individual XP (1-3 Players)	Individual XP (4-5 Players)	Individual XP (6+ Players)
APL − 8	25	10	5	5
APL − 7	35	10	10	5
APL − 6	50	15	15	10
APL − 5	65	20	15	25
APL − 4	100	35	25	15
APL − 3	135	45	35	25
APL − 2	200	65	50	35
APL − 1	300	100	75	50
APL	400	135	100	65
APL + 1	600	200	150	100
APL + 2	800	265	200	135
APL + 3	1,200	400	300	200
APL + 4	1,600	535	400	265

To design an encounter under this system, follow these steps:

1. Determine APL. Use the method from the standard rules, but do not adjust the APL by the number of PCs. That adjustment will be factored in as part of Step 2.
2. Determine CR. To find the proper CR for the encounter, decide how difficult you want the encounter to be for the PCs, and then consult Table 2. Find the column with the number of players in your group. Then look up the desired encounter difficulty to find the appropriate CR.
3. Determine XP Budget. Look up the XP budget for the encounter CR under the Total XP award column in Table 1. Even if you are using individual XP awards in your actual game, you should use the Total XP values to build encounters because those numbers are more mathematically consistent than the ones for Individual XP.
4. Choose Monsters. Choose any number of monsters whose XP values on Table 1 add up to the encounter's XP budget, based on their CRs relative to the APL.

Table 2: Encounter Design

Difficulty	CR (1-3 Players)	CR (4-5 Players)	CR (6+ Players)
Easy	APL − 2	APL − 1	APL
Average	APL − 1	APL	APL + 1
Challenging	APL	APL + 1	APL + 2
Hard	APL + 1	APL + 2	APL + 3
Epic	APL + 2	APL + 3	APL + 4

Example

Jill wants to build an encounter for her party of six 5th-level characters. She consults Table 2 and finds that an average encounter for a party of six or more players is equal to APL + 1. Thus, she needs a CR 6 encounter. Looking at Table 1, she sees that she has 600 XP to spend on this encounter. She could use one CR 6 (APL +1) monster to fill the entire budget at once, or she could use any combination of multiple monsters whose XP award adds up to 600. She decides on a two-monster encounter, using a troll (CR 5, equal to APL; 400 XP) and an ogre (CR 3, APL − 2; 200 XP).

Creatures With Fractional CRs

To use a creature with a fractional CR, find the difference between CR 1 and the APL, and use Table 1 to find the appropriate XP value. This XP value applies to a number of the creatures equal to the denominator of its fractional CR (two for a CR 1/2 creature, three for a CR 1/3 creature, etc.). If you want more creatures than that number, use the CR Equivalencies table from the standard rules to find the appropriate XP value.

For example, Jill wants her six 5th-level PCs to be attacked by orcs (CR 1/3) in an easy (CR 5) encounter. CR 1 is four below the APL of 5, so three orcs are worth 100 points. Because she wants the entire encounter to consist of regular orc warriors whose leader isn't around, she consults the CR Equivalencies table from the PRD and finds that four creatures combine to make one creature of four times one creature's CR. Since each "creature" in this situation is three orcs, it takes 12 orcs to fill out the encounter.

Using Weaker Creatures

If you want to use creatures whose CR is less than the APL − 8, use the CR Equivalencies table mentioned above to find a number of creatures of an appropriate CR that is covered by Table 1. If the creatures are extremely weak, you may have to chain together multiple uses of the CR Equivalencies table to find the desired number of creatures.

For example, if Jill's PCs have advanced to 10th level and she wants to create an average (CR 11 for Jill's six-person party) encounter involving bugbears (CR 2), she would look on the CR Equivalencies table and find that two bugbears are equivalent to a CR 3 monster (APL − 8 in this case), and the table covers up to 16 bugbears at CR 9 (APL − 2). Jill could fill an entire average encounter for this group (CR 11) with bugbears by using 32 bugbears (CR 9 + 2 = CR 11; 16 bugbears × 2 = 32 bugbears), or use that number of bugbears as part of a more difficult encounter.

Optional XP Award Method

This system can make it impossible for PCs who are behind the APL to catch up, except in groups where different players often miss sessions for different reasons. Therefore, if the PCs are not all the same level, you may want to use the following method instead of the one in the standard rules.

This alternate method has one version when using Total XP and another when using Individual XP. If you are using Total XP for experience awards, look up the amount of XP for the encounter CR in relation to each character's total level, not the APL. Then give each player the Total XP award for his or her level divided by the number of party members.

For example, if a party consisting of four 5th-level characters and one 4th-level character (for an APL of 5) defeats a CR 5 encounter, the GM gives the four 5th level characters 80 XP each for the encounter (400 XP for a CR = character level encounter, divided by five party members). The lone 4th level character gets 120 XP (600 for a CR = character level + 1 encounter, divided by five party members).

The Individual XP method is easier. First, find the row in Table 1 corresponding to the encounter CR in relation to the character's total level. Then, give the character the Individual XP award for the number of characters in the party. For the party above, the four 5th-level characters would get 100 XP each, while the one 4th-level character gets 150 XP.

Benefits of Rollover XP

The Rollover XP system offers more than just smaller XP budgets for high-level encounter design. Because the number of XP required to advance is the same for any level on a given XP track, Rollover XP allows a group to smoothly switch between XP tracks in the middle of a campaign. Thus, a GM who likes to get players through the first couple of levels quickly could decide to use Fast advancement for Levels 1-3 and Medium advancement for the rest of the campaign. Or a GM whose group prefers mid-level play could use Medium advancement until 5th level, and then switch to Slow advancement. Other GMs or groups could combine both these approaches, or use other complex sequences of advancement rate shifts over 20 levels.

I feel that this new level of flexibility is the major benefit of Rollover XP. While the standard PFRPG rules do a good thing by giving groups multiple explicit, defined rates of advancement, this advancement system gives PFRPG GMs total flexibility in determining how fast they want the PCs to advance.

House Rule Review #1: Character Creation

This is the first in a series of posts analyzing some house rules for d20 fantasy gaming that I wrote and later abandoned. I debated how to approach this topic and what information to include, so it took longer to finish than I initially promised. In the end, this post became more complicated and the series will now be only three posts. This is because the material from the fourth chapter, "GM Tricks" works better when integrated into the other posts than when presented in its own post.

When I first read the D&D 3.0 core books, I liked the fact that the designers included a point-buy system for ability scores. D&D 2e was designed on the assumption that everybody would roll their characters randomly, and it was hard (even for the designers of Player's Option: Skills and Powers) to come up with a point-buy system that didn't make life miserable for classes that had ridiculous entry requirements, like the ranger and paladin.

However, my excitement was tempered by the fact that the number of points given to create a character in this system seemed too low. It just seemed like 25 points was too few to make a really heroic character. The characters I made with 25 points in that system also seemed to pale in comparison to most characters I randomly rolled using 4d6-drop-the-lowest.

The internet agreed with me. In a thread on the old WotC boards dedicated to crunching the character creation numbers, one user ran a computer program that found that, when the 3.x hopeless character rule was taken into account, the average rolled PC's stats were worth 29-30 points on WotC's table.

When WotC moved on to 4e and another company took up the mantle of "traditional" d20 fantasy gaming, I was eager to see what happened to point buy. It turns out that the PRD "purchase" system uses a table that scales more harshly than the old WotC table. Furthermore, there seems to be no relation between the default random method and the Standard Fantasy point value. In other words, 15 points on the PRD table is as bad as 25 on the D&D 3.x table.

My Old Solutions

In my abandoned house rules, I wanted my random and planned character creation methods to be roughly equal in power level. The goal was to have different power levels, each with a random method, a point-buy number, and a default array, with the point-buy value and the array roughly equal in power to the average character created by the die roll method. It was an ambitious undertaking, and I did a lot of math and a lot of online research into sites like this one to make things match up.

In the end, I got frustrated trying to come up with default arrays, especially after I decided to try to give two per power level: one with no weaknesses and another with a weakness and a higher top ability score. I decided it would be easier to accomplish this design goal in a system that didn't have the 3-18 range of scores, and at that point, I was basically making another game, and not just houseruling an existing one. Of course, I was almost going down that road anyway, since I made my own point-buy table for those rules.

I abandoned the idea of making my own point-buy table for my potential campaigns, since I didn't think I'd ever find a group of players who would try it. I also abandoned my first system for figuring out how many points to give for each power level. However, I've since come up with a new system for that.

My New Solution

The key to my new system for finding point buy numbers is calculating the cost of a spread of ability scores centered on the average for a given random method. The weakness of even the most thought-out point-buy systems was that they calculated the cost of buying the average ability score six times, and rolling a character rarely gives you a set of scores that close together. Thus, those systems create radically underpowered characters.

The system I finally settled on is described here. As an example of the system in action, I will find the point value of the standard 4d6-drop-the-lowest method for the PRD Purchase Table (spoiler alert: it's not 15 points). However, this method works with the SRD table or any other point-buy table for a d20 game.

1. Find the average die roll of your random method. You can use any number of online tools to do this. A simple tool can be found here. If you're comfortable writing code, you can also use AnyDice. The average die roll for the standard 4d6 method is 12.24.
2. Add the point values for the whole number part of the average and the three scores above and below that number. For 12.24, we drop the .24, keep the 12, and add the point values of 9, 10, 11, 12, 13, 14, and 15. These values are -1, 0, 1, 2, 3, 5, and 7. The total is 17.
3. Multiply the result of Step 2 by 6/7 and round the result to the nearest whole number. In our example, 17 x 6/7 = about 14.57, which rounds up to 15.
4. Repeat Steps 2 and 3 for the number above the one you used in Step 2. In this case, the next higher number is 13, so we add the point values for 10, 11, 12, 13, 14, 15, and 16. Those values are 0, 1, 2, 3, 5, 7, and 10, for a total of 28. Twenty-eight x 6/7 is 24.
5. Multiply the fractional part of your average die roll by the difference between the numbers from Step 4 and Step 3. The difference between 24 and 15 is 9. Nine x 0.24 = 2.16.
6. Add the results of Step 3 and Step 5 and round the result to the nearest whole number. In our example, 15 + 2.16 = 17.16, which rounds down to 17. Our point value for the standard character creation method (4d6, drop the lowest) is 17.

This method has a couple of potential weaknesses. While it generally gives more accurate point values than official sources for any d20 game, it still somewhat underrates point values when used on a steeply scaling table (like the PRD table). However, depending on how highly you rate the power of picking your scores, you may see this quirk as a feature, not a bug.

Blast From the Past

I stumbled on a printed-out manuscript of some old house rules I made up for Pathfinder. That project started out as a bunch of small changes I was going to make to the rules, but the changes grew to the point where I figured I might as well write my own game instead of expressing my changes as a set of house rules. That's when I started work on my own personal d20 heartbreaker, combining elements of Pathfinder and True20 into an unholy mishmash.

Over the last few years, I've refined some of the assumptions behind those house rules. However, since I'm trying to get back into blogging and other forms of writing, I figured I'd do a series of posts on those old rules, the good and bad points about them (as I see it), and some new rules incorporating some ideas from those house rules. I hope to do a post on each chapter of that manuscript. Following the sequence of chapters, the topics, in order, will be:

1. Character Creation (die rolls, point buy, and default arrays)
2. Classes (with an emphasis on the core classes)
3. Gamemastering (encounter and NPC design, plus character advancement, for reasons to be discussed later)
4. GM Tricks (ways to make these house rules waaay more flexible than the standard game)

The first post might be coming later this week, and I'm going to try to get these posted in fairly rapid succession (at least compared to my usual turtle-paced writing).