Today I saw a thread on one of the forums discussing the d30 and what it was used for. The thread actually produced a couple of useful suggestions. Additionally, we have used a d30 for our own purpose for quite some time and I thought it was worth describing here in full detail.

Calendar Related Uses

One obvious use is to determine the day of month. Or, in conjunction with a d12, determine the day of the year. A particularly useful application of this would be to determine a character’s date of birth. Obviously, this means having to re-roll the 29th and 30th of February and forego the possibility of any births on the 31st of any month, but otherwise this works out very nicely.

In the forum thread that sparked this post, someone suggested that a d30 can be used immediately after a character is bitten by a werewolf to determine when the next full moon would be. Although rolling a d30 is an excellent way to determine a day of the month, a werewolf bite that infects a character must be presumed to occur during a full moon. Therefore, rolling to see when the next full moon will occur seems a bit unnecessary. :)

A Specialty Roll

Any of a number of reasons (a spell, class ability, benefit from an item, etc) could allow a character to replace a single d20 roll with a d30 roll, offering an increased chance of success. A magical set of lock picks could allow a thief to roll a d30 instead of a d20 when using them to pick a lock. Dwarves are particularly resistant to poison. Instead of giving them a bonus to saves versus poison, they instead could be allowed to roll a d30 to make such saves. There are spells that give the recipient a bonus to hit. Instead, the recipient could be allowed to roll a d30 for attacks for the duration of the spell. Any d20 roll could similarly be replaced with a d30 roll. This gives an increased chance of success but still allows room for failure. Used in moderation, this shouldn’t have any serious impact on the game.

What Does This Gain?

Nothing really. It’s not like there is something broken that needs to be fixed. It’s just for fun. Adding a static bonus to something may be helpful, but using a d30 in place of a standard d20 for some special purpose adds a feeling of excitement.

What We Use a d30 For

One member of our group has been running a 1e game for some 30+ years. One session we had an unusually long run of bad rolls. The monsters would miss, the characters would miss, the monsters would miss… it seemed like combat lasted forever.

As an experiment, he decided to use a d30 for all attack rolls. I had some reservations, thinking that this would simply result in everyone hitting all the time basically defeating the whole purpose behind rolling to hit.

But that isn’t how it worked out at all. Naturally everyone did hit more often. But everyone also continued to miss considerably often as well (at least on tougher ACs). The fighter characters and higher level monsters were already hitting most of the time (except for that long unlucky streak I mentioned) so the change in their case really wasn’t very noticeable. Non-fighter characters and low-level monsters (two groups that always missed quite frequently) were now hitting about half again as often as before. They still missed quite a bit but not nearly as much.

It’s always disappointing to miss but missing round after round every combat is more than just annoying. By upping the hit frequency, it made it more fun for non-fighters forced into melee. Even though the low-level monsters were also hitting more often, this wasn’t a bad thing. Fighting an opponent that misses every round isn’t a challenge and becomes boring quickly. Now, when a 7th level party had to clear out a large infestation of Orcs, it wasn’t merely a chore of tallying how many dropped each round. Now the Orcs were able to hit back which added a level of excitement to a fairly insignificant encounter.

Balance Issues

Clearly, the obvious concern is how this change will affect the balance of the game. I haven’t run extensive numbers on the effects of this change, nor have we tested it at all levels. However, after a number of years of using this method in his games, we have not run into any troubles. Since everyone is using d30 attack rolls across the board, I don’t think that any balance issues will ever arise.

Why Don’t I Use It?

I’ve never adopted d30 attack rolls in my own games. Primarily this is because I have never bothered to purchase any d30 dice. Maybe it’s because I like d20s and don’t want to give them up. Maybe it’s because this is someone else’s house rule and it wouldn’t feel right to steal someone else’s rule. In part, I’m sure it’s because d30s roll longer than d20s. For a player, the amount of time is negligible. For a DM, that has to roll for a number of creatures each round, that time adds up. Still not a big deal, but that’s certainly part of it.

Being forced to look at it more closely today, I’m wondering if I want to make the switch. I am certainly tempted.

Critical Hits

This is the issue that tempts me the most towards switching to d30 attack rolls. Rolling a 20 on 1d20 occurs roughly 5% of the time. With five players or so, as many monsters, and multiple attacks, this can result in a possible crit once every round or so. If you adopt weapons and feats that allow a wider threat range, crits begin happening far more frequently than I think they should. By switching to a d30 attack roll, potential crits appear only two thirds as often. This change reduces them back to where I feel they belong. It also makes them feel more special when they occur.