Roll to Hit

Roll to hit refers to the d20 die roll required to successfully strike an opponent, whether using a weapon, physically touching an opponent, or launching a magically propelled force, such as Melf's arrow or spiritual hammer. The outcome of this roll is determined by THAC0, a system that calculates the chance to hit based on the attacker's experience level and the opponent's armour class (AC).

A roll of 1, 2, or 20 carries special significance, invoking the rules for critical hits and fumbles. These outcomes can dramatically affect combat, making such rolls noteworthy regardless of modifiers.

Penalties and bonuses to hit are applied either by modifying the die roll directly or by adjusting the number needed to hit. These modifiers are influenced by a variety of conditions, spells, and environmental factors. Below is a detailed list of common modifiers, which expand upon how these rules interact with the mechanics of AD&D:

• Attacks with Two Weapons: When using a weapon in each hand, the attacker incurs penalties based on their dexterity and other relevant stats. These penalties reflect the difficulty of coordinating dual attacks.

• Charging: Charging into combat grants a bonus to hit and damage but may expose the attacker to counterattacks, depending on terrain and other circumstances.

• Cover: Defenses such as walls, vegetation, or natural terrain offer modifiers to the defender's AC. The degree of cover—partial, three-quarters, or total—determines the level of protection.

• Dexterity: This stat affects attack rolls when using missile weapons, providing bonuses or penalties depending on the attacker’s dexterity score.

• Grenade-like Missiles: Attacks with items like grenades or flasks often target an area rather than a specific defender. In such cases, the attacker rolls to hit AC 10 for a direct effect, with deviation determining the actual impact location.

• Groggy: Characters suffer a -2 penalty to attack rolls when they have just awakened from sleep. This reflects their disorientation and sluggish reflexes.

• Helpless Defenders: Creatures that are magically held, paralyzed, or asleep can be struck without requiring a roll to hit. In such cases, damage is applied automatically. If the damage disrupts the spell affecting the defender, such as through a dispel magic effect, the defender may be freed or awakened.

• Illumination: The level of lighting significantly impacts combat. Dim light or darkness imposes penalties to hit, especially when using missile weapons. Bright light ensures normal accuracy.

• Invisibility: Attacking an invisible opponent is nearly impossible without detection. Characters with heightened senses may locate an invisible defender by sound or other subtle cues, allowing attacks at -4 to hit. Creatures with a translucent shimmer are attacked at -2. AD&D rules do not apply a percentage-based bonus to identifying invisible opponents based on level.

• Magic: Numerous spells provide attack and defense modifiers. Defensive spells include protection from malevolence, barkskin, stoneskin, armour, and phantom armour. Offensive spells requiring a roll to hit include Melf's arrow, spiritual hammer, chromatic orb, magic stone, and shocking grasp. These spells generally ignore armour and target AC 10. Spells that enhance physical abilities, such as strength or enchanted weapon effects like flame blade or shillelagh, roll to hit as usual.

• Multiple Defenders in One Hex: When attacking a hex containing two defenders (neither trained in Puissance), the attack roll gains a +2 bonus due to the crowded conditions.

• Paladin Class: Paladins benefit from a continuous protection from malevolence effect, imposing a -2 penalty on attack rolls made against them.

• Rear & Flank Attacks: Attacks made from the rear gain a +2 bonus. Thieves and assassins striking from behind during a surprise attack gain an additional +4 bonus. Flank attacks receive a +1 bonus.

• Strength Ability: Strength bonuses or penalties affect attack rolls when using melee weapons, based on the attacker's strength score.

• Missile Ranges: Attacks made with missile weapons are influenced by distance. Shots at close range (2 hexes) gain a +1 bonus, while medium-range attacks suffer a -2 penalty, and long-range attacks are made at -5.

See Attacking in Combat