Does it destroy the system to use d6s insteads of d20s in Donjon?
I just don't have that many d20s...

Nope, should work fine. It CHANGES the game though. You will get ALOT more tied high dice (for obvious reasons) resulting in fewer multiple successes (because more dice will get discarded). But you'll also have fewer times where you roll good everything 12-18, but your opponent who rolled all low except for a single 20 wins.

I used d10s when I played Sorcerer (which inspired the Donjon mechanics). I'd recommend them over d6s if you have them.

The one other problem is initiative in combat, which pretty much depends on d20's.

What I would recommend, if you insist on using a different die size, is the following fix for initiative:

- Everyone rolls initiative per normal with the new die size.

Example: I have a Dis of 4 and am Level 5, so I roll 9 d10's:
[2, 3, 3, 3, 5, 6, 6, 8, 10]

- When initiative is tied, characters go in order of Adroitness.

Example: Bob (another player), one of the GM's orcs, and I all go on 8. Bob has an Adr of 5, I have an Adr of 4, and the orc has an Adr of 3. Bob goes, then me, then the ork.

- If someone has more than one action on a number, everyone goes once, then that person can go again.

Example: I rolled 3 three's. Bob rolled one three, and the orc rolled two.

Order: Bob goes, I go, the orc goes, I go, the orc goes, I go.

(Note: In play, I never do any of this. Really.)

Thanks, I'll use that initiative rule.

However, I don't have enough d10s either. I'm stuck with d6s. Do you think the following rule would help balance things?

In the case of a tie, set those dice aside. Then determine the winner as normal. That person gets to count the ties as successes.
For example:
Player rolls 6 dice: 1,3, 4, 4, 5, 6
GM rolls 7 dice: 1, 1, 3, 4, 5, 5, 6
After setting aside the two ties, the GM wins with one die. That means he gets a total of three successes.

Out of curiousity, I took a program I built to estimate Donjon dice probabilities and modified it support selectable dice types and for choosing whether to discard ties or count them towards successes.

Discarding Ties

The end result is that the size of the die doesn't matter much in most situations. The difference becomes most apparent when one side has a much larger number of dice (on the order of 300% or more), where the difference in the overall chance of success was as much as 8 or 10%, where using smaller dice favored the side with more dice. As an example, 10 dice versus 2 dice, with d6, the chance of achieving any success for 10 dice is overall 93%, while using d20s it's only 87%. When the number of dice were the same, or close to the same (6 versus 5, 10 versus 8, etc), the difference was negligable, no more than a percent or two for any given number of successes or failures, and only 2% or 3% overall for success/failure. Overall, smaller dice tend very very slightly to increase the average number of successes, but the difference is probably not really noticable in play.

Keeping Ties as Successes for the Winner

Here, the difference was much more noticable. The overall chances of success didn't change radically, as expected, but the average number of successes did, quite a bit, moving the weighted average number up very significantly, especially with larger numbers of dice. At 6 dice versus 6 dice, the difference from an average of 1.88 successes with a d20 to 2.44 successes with d6. With 20 dice against 20 dice, it goes from 2.68 to 5.19, on average. However, the difference decreases fairly dramatically as the difference between the number of dice rolled on each side goes up: At 9 versus 6 dice, the difference between d6 and d20 is 3.15 compared to 2.37. For 16 versus 3 dice, the difference a 'mere' 5.79 to 4.99 for d6 vs d20. When keeping ties as successes, the mode number of successes seems to be 2, whereas it's 1 when not keeping them.

In summary

If you don't switch to keeping ties as successes, then changing the number of sides on the dice doesn't make a very big difference in the overall results of the game. It may feel different, due to the larger number of ties, but the end results will be just about the same. During the playtest session I just got to play in, the most common sort of roll seemed to be in the range of 4 to 10 dice verses 3 to 9, probably right around 6 versus 6 on average, if I had to guess, so the difference in wildly disparate contests won't affect things so much.

If you switch to counting ties as successes, things change a bit, but not enough, I think, to make the game completely different. On the whole, there will be more successes, giving more shared narrative control in the form of facts and what not, even though the overall chance of success for any given task won't change that much.

-DaR

Oh, I forgot to qualify my statement. It doesn't change the game for general rolls. Initiative is still something of an issue, but Clinton already addressed that in his post.

-DaR

Thanks for your detailed analysis, DaR, very helpful. This tells me that Ron's decision in Sorcerer to leave the dice up to the player was a totally reasonable one, and that I can play Donjon with d6, since no way in hell am I ever going to own more d20 than d6! :)

--TQuid

Just a note. I was very skeptical of d20s before we actually played with them. We originally put them in the rules because it was funny to say "more d20s than any other game."

But then, after playing with d20s, I can't imagine using another die. It just feels right.

Clinton R Nixon wrote:
- Everyone rolls initiative per normal with the new die size.
...
- When initiative is tied, characters go in order of Adroitness.

OK, I just purchased 15 d20s, bringing my total up to 19. I'm good to go.
(By the by, would this be enough for me and a few players, since they may not have many d20s of their own?)

Also: should I run the game where they slaughter their way through a zoo searching for an errant coffin; or a standard cave-bashing orc-butchering dungeon-crawl?

I like the first cos it's cool. I like the second because it feels like DnD, which, (hopefully), will emphasise how much funner (sic) Donjon is than Dungeons and Dragons. So which should I got with?

Points to bear in mind: the players do not know me. It is their club, I am a newbie to it. They are hardcore Dungeons and Dragonists. I want to introduce them to indie games; if this goes well, I earn their trust and can try new things in future weeks. If it goes badly...

I'm playing tomorrow afternoon, so prompt replies would be appreciated.

Nomad wrote: OK, I just purchased 15 d20s, bringing my total up to 19.

You should give em' something basic, but give them a few twists to it. Make sure everyone gets a Narration type skill, and it may not hurt to "suggest" occasional uses of it. Other cool skills such as breath fire, or fun stuff is cool as well.

You might even want to take it to an all monster pc party("Let's see, drow, vampire, death knight, beholder, and a elemental, ok, let's pick abilities!"), just to show off the range of ability in the system :)

Clinton, what was the easiest and hardest for the new folks in Gamestorm to grasp? It might help out.

Chris

Strangely, the thing I had to prompt people most about at Gamestorm was "combos," or using successes to add more dice to your next roll. Most people usually wouldn't remember that they were much more effective this way.

For example, the monk had an average combat ability, but an amazing Leap ability, and an Attack from High Places ability. Still, she chose just to hit things more often than not. When I would remind her, she was much more effective in combat.

One more thing - the all monster party is awesome. I've been wanting to do that myself - create a party of random monsters and have them protect their home from maruading adventurers.

Clinton R Nixon wrote: One more thing - the all monster party is awesome. I've been wanting to do that myself - create a party of random monsters and have them protect their home from maruading adventurers.