1. Armour Class (AC): This is the measure of how difficult it is to land a successful hit on a character or creature in combat. Higher AC values mean a target is harder to hit.

2. Base AC: This is the starting AC for a creature or character before any equipment, spells, or other modifiers are applied. For a player character without any armor or shields, the base AC is typically 10.

3. Armor Bonus: The bonus to AC provided by wearing armor. Different types of armor provide different bonuses.

4. Shield Bonus: This is the additional bonus to AC provided by using a shield. Like armour, different types of shields provide different bonuses.

5. Dexterity Modifier: In addition to armour and shields, a character's Dexterity modifier can also affect their AC, representing their ability to dodge attacks.

6. Natural Armour: This is a bonus to AC that certain creatures have due to their tough skin, scales, or other natural defences.

7. Deflection Bonus: Certain magical effects can provide a deflection bonus to AC, representing a force that turns attacks away.

8. Size Modifier: Smaller creatures are harder to hit than larger ones, so the size of a creature can provide a modifier to AC.

9. Touch AC: Some attacks bypass armour entirely and target "touch AC" instead. This AC doesn't include any bonuses from armour or shields.

10. Flat-Footed AC: This is the AC of a character who hasn't had a chance to react to a threat yet, such as at the beginning of combat or when surprised. It doesn't include any bonuses from Dexterity or other sources that require the character to be aware and able to move.

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Armour Class In Depth

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The Armour Class, commonly referred to as AC, is a pivotal component in the Dungeons & Dragons gameplay system. It signifies the difficulty to land a successful hit on a character or creature during combat. A higher AC value implies a target is more challenging to hit, thus enhancing a character's survivability.

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At the heart of calculating AC lies the Base AC, the raw defensive value before considering any external factors. This is the starting AC for a creature or character before incorporating any adjustments from equipment, spells, or other modifiers. Typically, for a player character with no armour or shields, the Base AC stands at 10.

Armor Bonus is a critical factor that modifies the Base AC.

 

By donning armour, a character adds a protective layer that could deflect or absorb incoming attacks, thus enhancing their AC. Different types of armour provide varying bonuses, with heavier armours typically offering greater defence but often limiting the wearer's mobility or imposing other trade-offs.

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Similarly, shields contribute to a character's defensive strategy by providing a Shield Bonus. Like armours, shields come in various types, each offering a different degree of protection. A character must wield a shield to benefit from its AC boost, often at the cost of forfeiting the use of that hand for other purposes.

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A character's agility and reflexes, represented by the Dexterity Modifier, also play a part in determining the AC. A nimble character could dodge or deflect incoming attacks, thereby reducing their chance of being hit. Hence, the Dexterity modifier is often added to the Base AC, assuming the character's armour allows for such manoeuvrability.

Natural Armor is an inherent AC bonus that certain creatures possess due to their biological defences, such as tough skin, scales, or thick fur.

 

This bonus is a built-in component of the creature's Base AC, making them naturally more resilient.

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On the more mystical side, magical effects can yield a Deflection Bonus to AC. These effects represent protective forces that deflect attacks away, whether they stem from spells, enchanted items, or divine blessings.

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The size of a creature, represented by the Size Modifier, also impacts the AC. Smaller creatures, being harder targets to hit, often have a positive size modifier added to their AC, whereas larger creatures are easier targets and might suffer a penalty.

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However, not all attacks aim at the full AC. Some, instead, target the Touch AC, bypassing the protection offered by armour and shields. These attacks typically involve spells or effects that merely need to touch the target to take effect, making the character's physical defences irrelevant.

 

Finally, the Flat-Footed AC represents a character's vulnerability when they haven't had a chance to react to a threat yet, such as at the beginning of combat or when caught off guard. This AC calculation disregards any bonuses from Dexterity or other sources that require the character's awareness and ability to move, making surprise and initiative vital factors in combat scenarios.

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In essence, the system of Armour Class in D&D encapsulates numerous factors, reflecting the complexity and variability of combat scenarios. Understanding these components is key to mastering the art of defence.