All creatures in ITD&TD have 6 Ability Scores: Strength, Dexterity, Constitution, Intelligence, Wisdom, and Charisma. Each of these scores help determine your character's overall ability to do things.
These scores are listed as numbers between 1 and 30. Ability Scores are not used often, and when they are it is frequently outside of dice rolls. Instead, you apply ability score modifiers. Ability Score Modifiers are what you apply to d20 tests when applying a particular ability score.
For example, a creature with a Strength Score of 13 has a Strength Modifier of +1. Anytime they make a d20 test using Strength, they can add a +1 to the roll.
| Score | Modifier | Score | Modifier | |
|---|---|---|---|---|
| 2 | -4 | 8 - 12 | 0 | |
| 3 | -3 | 13 - 15 | +1 | |
| 4 - 5 | -2 | 16 - 17 | +2 | |
| 6 - 7 | -1 | 18 - 19 | +3 |
Your ability scores can apply to a wide range of things, but players and GMs should strive to use the right ability score for the right task. For example, if you are attempting to listen at a door, you should use a Wisdom skill test, not a Strength skill test.
Strength should be used in cases where Physical Force is the primary means of getting something done. Climbing cliffs, jumping long distances, attacking with melee weapons, or breaking down a door are all examples of Strength.
Dexterity should be used in cases where hand-eye coordination, or quickness are involved. Tight-rope walking, dodging an attack, firing a bow, picking a lock or moving silently are all examples of Dexterity.
Constitution should be used in cases where physical toughness or endurance are called into question. Staying awake for days on end, pushing through a march without food, holding your breath, or drinking large amounts of ale are all examples of Constitution.
Intelligence should be used in cases where your mental acumen and ability to recall knowledge are tested. Recalling a bit of lore, searching a for a secret door, estimate the value of an item, or determining how best to break down a door are all examples of Intelligence.
Wisdom should be used in cases where your insight and awareness are used to determine the outcome. Hearing the fine details of a conversation behind a door, hearing your name called in a crowd, or spotting an assassin before he strikes are all examples of Wisdom.
Charisma should be used in cases where your force of personality can affect others. Your ability to interact with others, your guile, your charm, and your persuasiveness are all examples of Charisma.