The original D&D dice were the 5 platonic solids, the 10s were added later. But there are lots of shapes that can be "fair". You can stick 2 pyramids with any number of sides together, you can make a long prism with any number of sides since it will never land on the long ends, a coin can be considered to be a 2 sided die. I seem to recall somebody made a 30 sided die where the sides were parallelograms, although I never had one.

> The original D&D dice were the 5 platonic solids, the 10s were added later.

True; IIRC, the rules used d10 but it was a way of reading the d20 before d10s were manufactured.

yup the original d20's were labeled 1-10 twice, and you used a crayon to colour the on set differently. If it landed on your "blue" 10 it was a 20, if it landed on the uncoloured 10 it was 10 for example.

Any regular bi-pyramid would be technically fair. I think it's just that you tend to get rounder dice by using platonic solids or tesselating / modifying platonic solids.

By the way, you can get d100 dice.

> By the way, you can get d100 dice.

Can you get fair d100s, though?

I know the “Zocchihedron”, one of the first and best known commercial ones, is not fair (after this was proven, they were renumbered so that the over-/under-weighted results were better distributed over the range, but it's still not fair.)

Yes. By trivial example, two fifty sided pyramids joined at the base. These can be purchased.

Most players use d10 pairs with a tens die, though, because they roll better.

> Most players use d10 pairs with a tens die, though, because they roll better.

There's also a nifty trick used in many RPGs based on d100 to roll once and have 2 d100 numbers (by inverting the result).

So for example in Warhammer you roll d100 for attack, you hit if your result is lower than your Melee Combat attribute, and the inverted result shows which part of the enemy body you hit (that influences critical hits and armor).

Also a 100-sided cylinder. Probably hard to read though.

Do you have a link for the pyramid one?

No. I bought it 25 years ago in a game store called "Games Unlimited" in Pittsburgh, PA.

Wow, I'd seen one but never actually checked whether it was fair.

All that is required for fairness is equal faces and equivalent reach behavior.

Every total symmetry fits. You don't need a platonic solid. By example, every even number six or up can be fairly represented as two pyramids joined at the base.

Many fair non-platonic dice exist besides the d10, such as the d30. Go ask at the game store

I actually own a d30, as well as a super weird looking d3. But you don't generally see non-platonic solids for anything but a d10. Why? My guess was ease of manufacture, but honestly IDK.