The weapon die or dice (abbreviated [W]) of a weapon determines the damage of attacks using that weapon.
For example, a longsword's damage die is 1d8, meaning you roll one 8-sided die for attacks that deal 1[W] damage, or three 8-sided dice (3d8) for attacks that deal 3[W] damage.
Weapons with multiple dice are multiplied in a similar way. For example, a falchion's damage dice are 2d4, so roll 6d4 for attacks that deal 3[W].
The weapon dice are intended to be used for weapons used by small or normal characters. Large, Huge and Gargantuan creatures need to use weapons specially sized for them, with the larger weapons having their dice increased by one step each time.
If it is necessary to adjust the weapon die due to size or for other reasons, it is adjusted as below:
- One-handed: 1d4 -> 1d6 -> 1d8 -> 1d10 -> 1d12 -> 2d6 -> 2d8 -> 2d10
- Two-handed: 1d8 -> 2d4 -> 1d10 -> 1d12 -> 2d6 -> 2d8 -> 2d10