Game Dice

In these rules, the different dice are referred to by the

letter d followed by the number of sides: d4, d6, d8, d 10,

d 12, and d20. For instance, a d6 is a six-sided die (the

typical cube that many games use).

Percentile dice, or d 100, work a little differently. You

generate a number between 1 and 100 by rolling two

different ten-sided dice numbered from 0 to 9. One die

(designated before you roll) gives the tens digit, and

the other gives the ones digit. If you roll a 7 and a 1, for

example, the number rolled is 71. Two 0s represent 100.

Some ten-sided dice are numbered in tens (00, 10, 20,

and so on), making it easier to distinguish the tens digit

from the ones digit. In this case, a roll of 70 and 1 is 71,

and 00 and 0 is 100.

When you need to roll dice, the rules tell you how

many dice to roll o f a certain type, as well as what modifiers

to add. For example, “3d8 + 5” means you roll

three eight-sided dice, add them together, and add 5

to the total.

The same d notation appears in the expressions “1d3”

and “1d2.” To simulate the roll of 1d3, roll a d6 and

divide the number rolled by 2 (round up). To simulate

the roll of 1d2, roll any die and assign a 1 or 2 to the roll

depending on whether it was odd or even. (Alternatively,

if the number rolled is more than half the number of

sides on the die, it’s a 2.)

The D20

Does an adventurer’s sword swing hurt a dragon or just

bounce off its iron-hard scales? Will the ogre believe an

outrageous bluff? Can a character swim across a raging

river? Can a character avoid the main blast o f a fireball,

or does he or she take full damage from the blaze? In

cases where the outcome of an action is uncertain,

the Tir Na Nog’s game relies on rolls o f a

20-sided die, a d20, to determine success or failure.

Every character and monster in the game has capabilities

defined by six ability scores. The abilities are

Strength, Dexterity, Constitution, Intelligence, Wisdom,

and Charisma, and they typically range from 3 to 18

for most adventurers. (Monsters might have scores as

low as 1 or as high as 30.) These ability scores, and the

ability modifiers derived from them, are the basis for

almost every d20 roll that a player makes on a character’s

or monster’s behalf.

Ability checks, attack rolls, and saving throws are the

three main kinds of d20 rolls, forming the core of the

rules of the game. All three follow these simple steps.

1. Roll the die and add a modifier. Roll a d20 and

add the relevant modifier. This is typically the modifier

derived from one of the six ability scores, and it

sometimes includes a proficiency bonus to reflect a character’s

particular skill. (See chapter 1 for details on each

ability and how to determine ability’s modifier.)

2. Apply circumstantial bonuses and penalties. A

class feature, a spell, a particular circumstance, or some

other effect might give a bonus or penalty to the check.

3. Compare the total to a target number. If the total

equals or exceeds the target number, the ability check,

attack roll, or saving throw is a success. Otherwise, it’s

a failure. The DM is usually the one who determines

target numbers and tells players whether their ability

checks, attack rolls, and saving throws succeed or fail.

The target number for an ability check or a saving

throw is called a Difficulty Class (DC). The target

number for an attack roll is called an Armor Class (AC).

This simple rule governs the resolution of most tasks

in Tir Na Nog play. Chapter 7 provides more detailed rules for

using the d20 in the game.

In these rules, the different dice are referred to by the

letter d followed by the number of sides: d4, d6, d8, d 10,

d 12, and d20. For instance, a d6 is a six-sided die (the

typical cube that many games use).

Percentile dice, or d 100, work a little differently. You

generate a number between 1 and 100 by rolling two

different ten-sided dice numbered from 0 to 9. One die

(designated before you roll) gives the tens digit, and

the other gives the ones digit. If you roll a 7 and a 1, for

example, the number rolled is 71. Two 0s represent 100.

Some ten-sided dice are numbered in tens (00, 10, 20,

and so on), making it easier to distinguish the tens digit

from the ones digit. In this case, a roll of 70 and 1 is 71,

and 00 and 0 is 100.

When you need to roll dice, the rules tell you how

many dice to roll o f a certain type, as well as what modifiers

to add. For example, “3d8 + 5” means you roll

three eight-sided dice, add them together, and add 5

to the total.

The same d notation appears in the expressions “1d3”

and “1d2.” To simulate the roll of 1d3, roll a d6 and

divide the number rolled by 2 (round up). To simulate

the roll of 1d2, roll any die and assign a 1 or 2 to the roll

depending on whether it was odd or even. (Alternatively,

if the number rolled is more than half the number of

sides on the die, it’s a 2.)

The D20

Does an adventurer’s sword swing hurt a dragon or just

bounce off its iron-hard scales? Will the ogre believe an

outrageous bluff? Can a character swim across a raging

river? Can a character avoid the main blast o f a fireball,

or does he or she take full damage from the blaze? In

cases where the outcome of an action is uncertain,

the Tir Na Nog’s game relies on rolls o f a

20-sided die, a d20, to determine success or failure.

Every character and monster in the game has capabilities

defined by six ability scores. The abilities are

Strength, Dexterity, Constitution, Intelligence, Wisdom,

and Charisma, and they typically range from 3 to 18

for most adventurers. (Monsters might have scores as

low as 1 or as high as 30.) These ability scores, and the

ability modifiers derived from them, are the basis for

almost every d20 roll that a player makes on a character’s

or monster’s behalf.

Ability checks, attack rolls, and saving throws are the

three main kinds of d20 rolls, forming the core of the

rules of the game. All three follow these simple steps.

1. Roll the die and add a modifier. Roll a d20 and

add the relevant modifier. This is typically the modifier

derived from one of the six ability scores, and it

sometimes includes a proficiency bonus to reflect a character’s

particular skill. (See chapter 1 for details on each

ability and how to determine ability’s modifier.)

2. Apply circumstantial bonuses and penalties. A

class feature, a spell, a particular circumstance, or some

other effect might give a bonus or penalty to the check.

3. Compare the total to a target number. If the total

equals or exceeds the target number, the ability check,

attack roll, or saving throw is a success. Otherwise, it’s

a failure. The DM is usually the one who determines

target numbers and tells players whether their ability

checks, attack rolls, and saving throws succeed or fail.

The target number for an ability check or a saving

throw is called a Difficulty Class (DC). The target

number for an attack roll is called an Armor Class (AC).

This simple rule governs the resolution of most tasks

in Tir Na Nog play. Chapter 7 provides more detailed rules for

using the d20 in the game.