Welcome to the third installment of the House Rules column. In the first article, I discussed whether a house rule was necessary as a solution to your problem at the gaming table. In the second article, I discussed house rules that added something new to the game. Today, I want to discuss one of the most complicated types of house rule; modification.

Modifications are what we most often think of when someone says “house rule.” A modification is a rule that significantly changes the way the RPG is played by altering the official rules. Modifications need to be carefully considered and tested before being implemented because there are many issues, obvious and hidden, that occur when a modification is proposed.

Some examples of Modifications:

  • Condensing a skill list by collapsing skills together (both Mutants & Masterminds and Pathfinder have done this with the OGL skill list; I did it in the late 80s-early 90s with GURPS).
  • Allowing characters in AD&D to make an attack roll to parry an attack that would hit them.
  • Tripling hit points for 1st level D&D characters without doing the same for NPCs/Monsters.
  • Putting a cap on the number of points/ranks players may put into skills at character generation.
  • Streamlining d20 combat by removing attacks of opportunity.

There are some dangers to making modifications. Let’s take a look at a few:

Inadvertantly Nerfing/Powering-Up a Player Character

Many house rules are implemented during a campaign after an issue has been identified. Unfortunately, there may be established elements of the campaign, particularly on a PC’s sheet, that may be affected by the change, for better or worse.

For example, in d20 games, characters get a certain number of skill points based on their class. Condensing a skill list may make some characters good at almost everything. Conversely, if the skills are streamlined too much, then all characters will excel in the only skills they use, making a highly-skilled character unnecessary.

As another example, getting rid of Attacks of Opportunity in a d20 game may nerf certain feats or class abilities that are already on a character’s sheet or will significantly weaken a particular class.

Consolidation Means Power

While easily folded into the above category, I think skills are a special case (one Telas brought up in the comments of the last article), especially since some rules system actually encourage tailoring skill lists to your campaign.

The problem here is obvious, especially in point systems. If it used to take six skills to be an effective martial artist and it now only takes two then you have more points to spread around. More problematically, you could push those two skills higher than you would six (unless the skill cap was low enough that it had allowed you to raise all six to that level before). A social butterfly now needs less points to become a potent negotiator. A burglar may be able to bypass any security system with little difficulty.

Outperforming the NPCs

If there’s one thing I’ve learned as a GM over the years, it’s that the more options and special features you provide in the game, the less likely NPCs will use them. Players love options and will use them to their greatest advantage. As a GM, you have other things to worry about then whether your NPC throws a spin kick, side kick, crane kick, or flying fortress Immelman turn barrel roll kick to squeeze out the best tactical bonuses. As a result, the PCs could become significantly more powerful than their similarly-powered adversaries.

Modifying One Area of the Rules May Require Modifying Another Area

So you’ve decided to add Dodge and Parry actions during d20 combat. Are you planning on eliminating the Dex bonus to AC/Defense to compensate? How about lowering hit points? If you decide to give armor a Damage Resistance stat, will you eliminate its bonus to AC/Defense?

If you decide to modify a rule, make sure that it isn’t assumed somewhere else. In the above situations, Armor Class and Hit Points have traditionally represented multiple factors in combat. If you pull one of those factors out for a house rule and don’t compensate, then you may be threatening power creep or nerfing.

The Dreaded Die Roll

Both the 3rd and 4th editions of D&D have made combat more exciting with a variety of special moves and other factors. It can be difficult to recall the old days when a fighter simply rolled a die to hit with his favorite weapon and that was that (it’s also difficult to recall because many of us house-ruled additional combat options).

Sometimes, a rule modification can water down encounters. Maybe your players enjoyed having a lot of combat or social options, but now that you’ve trimmed them down the encounters are all feeling the same. Sure you could roleplay the distinctions, but after a while we all start taking the path of least resistance.

The Fun Factor

When modifying rules, never forget the fun factor. If the old rule was a bit broken but the players were having fun with it, they may not appreciate you tightening it up and sucking the fun out. Similarly, your new rule modification may make the game more unwieldly and, therefore, less fun (“Hey guys, I just made combat a lot more realistic! Oh, and, now it takes three times as long to resolve that fight against four kobolds).”

It’s Up to You

You may have noticed that I didn’t offer much in the way of solutions. That’s because every group is unique and what works for some won’t work for others.  Hopefully, I’ve highlighted some of the potential issues for you to think about when modifying rules.

How about you? Is there something I missed? Did you create a house rule that opened a new problem? If so, how did you address it?