Baldur Gate : Combat Basics

What is a 1d10 or 2d6 weapon?
Numbers like 1d10 and 2d6 refer to dice rolls used to compute weapon damage. 1d10 means 1 roll of a 10-sided die which equates to rolling a number from 1 to 10. 2d6 means 2 rolls of a 6-sided die which equates to twice rolling a number from 1 to 6 and combining the results. Thus 2d6 equates to rolling a value from 2 to 12 , i.e., (1-6) + (1-6) = (2-12).

The damage inflicted can be modified by such things as magical weapons, the strength of the attacker, weapon proficiency, other magical items, etc.:

  • DAMAGE modifiers due to magical weapons: Magical weapons may have modifiers which add damage to their standard damage roll. For example, long swords do standard damage of 1d8 (from Table 6, page 141 of the manual). The Long Sword +2 "Varscona" (see our Special Items page) has a rating of 1D8 + 2 (+1 Cold Damage). So when this weapon scores a hit, it will do damage of from 1 to 8 points (1 roll of an 8-sided die) plus 1 point of cold damage (assuming the enemy can be damaged by cold), or a possible total of from 2 to 9 points of damage. Note that this long sword also has a to-hit modifier, the +2 in the "1d8 +2" indicates an increased chance to hit (this will be addressed in the THAC0 question below).
  • DAMAGE modifiers due to character strength: Table 1, on page 134 in the manual, indicates damage adjustments for various character strengths. For instance, a character with strength 3 will inflict 1 less damage point (-1) when he hits whereas a character with strength 18 will inflict 2 more points of damage (+2).
  • DAMAGE modifiers due to weapon proficiency: The table on page 93 of the manual shows the bonus to damage due to level of weapon proficiency. For example, a proficiency of "Specialized" results in a bonus to damage of +2 whereas a proficiency of "Proficient" has no bonus to damage.
  • DAMAGE modifiers due to magical items: Magical items can also modify the damage you inflict. For example, the "Gauntlets of Weapons Expertise" (see our Special Items page) have a +2 damage bonus (will increase the damage you do by 2).
  • Other: There are also spells and potions that can increase combat damage.
What is Armor Class (AC)?
Armor class is your ability to keep from being hit, and in AD & D a lower AC is better (i.e.., A character with a -2 AC is much better off than one with a +6 AC). A defender's AC is combined with an attackers THAC0 to determine if the defender is hit. This will be discussed in the THAC0 question below.

Armor class can be modified in a number of ways:

  • Improved Armor: Table 8a, on page 142 of the manual, lists the base armor classes for various types of armor. For instance, Leather armor has a base AC of 8 whereas Splint Mail has a base AC of 4 (Splint, with the lower AC, is better than Leather). In addition, Table 8b, on the same page, shows how AC is modified against certain types of weapons. For example, Leather armor receives a +2 adjustment (8 + 2 = 10) if attacked by a piercing weapon whereas Splint receives a -1 adjustment (4 - 1 = 3) if attacked by a piercing weapon. Shields can also improve (lower) armor class.
  • Magic Armor: Some armors have magical properties. Studded Leather Armor +2 has a base AC of 7 which is reduced to 5, e.g. 7 - 2 = 5, due to the +2 enchantment.
  • Magical Items: Some magical items impart AC improvements. For instance, a "Ring of Protection +1" imparts, among other things, a +1 AC enhancement (i.e., wearer's AC is reduced by 1, e.g., 6 -1 = 5 ).
  • Dexterity: Table 1, on page 134 of the manual, shows how armor class is adjusted by the dexterity of the character. For instance, a character with dexterity of 3 would have his AC increased by 4 (the +4 is added to AC, e.g., 6 + 4 = 10) whereas a character with dexterity of 18 would has his AC decreased by 4 (the -4 is added to AC, e.g., [6 + (-4)] = [6 - 4] = 2 ).
  • Other: There are also spells and potions that can improve armor class.
What is THAC0?
THAC0 is an acronym for "To Hit Armor Class 0" and it is discussed on page 76 of the manual. However, that discussion is a little sparse, so I will embellish it with some information from AD&D 3rd addition rules.

Lower THAC0 is better! THAC0 is the MINIMUM roll you need to be able to hit an enemy with an armor class (AC) of 0 ( yes, lower armor class is also better as discussed above ). You must score a hit before you can do any damage!

When you attack an enemy, you SUBTRACT his AC from your THAC0 and the result is the minimum number you have to roll (on a 20-sided die) to be able to score a hit. To-Hit is always rolled on a 1d20 die (resulting in a number from 1 to 20). The BG manual states that a natural 1d20 roll of 20 ALWAYS hits (and will cause a critical hit), and a natural roll of 1 ALWAYS misses (where "natural" roll means an unmodified 1d20 roll). The BG manual also states that critical hits cause double damage!

Some examples:

  1. Enemy AC = 0, your THAC0 = 8 (including any to-hit adjustments) , your 1d20 roll must be equal to or greater than 8, (8 - 0 = 8), to be able to score a hit on the enemy. So you have 13/20 (13 out of 20) chances to hit.
  2. Enemy AC = -2, your THAC0 = 8 (including any to-hit adjustments) , your 1d20 roll must be equal to or great than 10, (8 - (-2)) = 8 + 2 = 10, in order to score a hit. So you have 11/20 chances to hit.
  3. Enemy AC = 5, your THAC0 = 8 (including any to-hit adjustments) , your 1d20 roll must be equal to or greater than 3, (8 - 5 = 3), to be able to score a hit. So you have 18/20 chances to hit.
  4. Enemy AC = 8, your THAC0 = 5 (including any to-hit adjustments) , your 1d20 roll must be equal to or greater than -3, (5 - 8 = -3). But how can you roll "-3"? Well, you cannot since the lowest value you can roll on a 1d20 die is "1"! So although the -3 result should indicate that you should score a "sure hit", there is still the rule that states that a roll of 1 is ALWAYS a miss, so your chance of hitting your enemy is actually 19/20 (19 chances out of 20), or you must get a 2 or higher on your 1d20 roll in order to hit your enemy.
The game displays your Adjusted THAC0. Each character class has a base THAC0 (see below) which changes with his experience level. This base THAC0 is adjusted by any THAC0 modifiers. For example, a level 3 warrior (with a base THAC0 of 18) is wielding a weapon with a +2 "to-attack" modifier, therefore his adjusted THAC0 would be 16 (18 - 2 = 16), and it is this adjusted THAC0 that would be used in calculating whether he was able to hit the enemy.

Generally, lowering your THAC0 by 1 will increase your chance by 1/20 of of hitting your enemy.

Your THAC0 changes based upon your character's class, type weapon wielding, type ammunition used in weapon (some arrows/missiles as well as slings and bows have +'s to attack), character's level (your THAC0 will decrease as you go up levels an amount depending upon character's class), weapon specialization skills, etc.

  • THAC0 modifiers due to weapon specialization: The table on page 93 of the manual shows the bonus "to-hit" for various levels of weapon proficiency. For example, a proficiency of "Specialized" results in a bonus to-hit of +1 whereas a proficiency of "Proficient" has no bonus to-hit.
  • THAC0 modifiers due to magical weapons and items: Some weapons are enhanced and have a bonus to-hit modifier. For an example, a 1d8 +2 weapon will lower your THAC0 by 2. There are also some magical items that can modify your THAC0. For example, the Gauntlets of Weapon Expertise (see our Special Items page) have a +1 THAC0 bonus (will lower your THAC0 by 1).
  • THAC0 modifiers due to strength: Table 1 on page 134 of the manual shows to-hit adjustments due to the strength of the character. For example, a character with strength 3 would have a -3 to-hit adjustment, i.e., his THAC0 would be increased by 3. A character with strength 18 would have a +1 to-hit adjustment, i.e., his THAC0 would be reduced by 1.
  • THAC0 modifiers due to Dexterity: . Table 1 on page 134 of the manual shows the missile weapon to-hit adjustment for dexterity. For example, a character with 3 dexterity would have -3 to-hit (missile) adjustment, i.e., his THAC0 (for missile attacks) would be increased by 3. A character with 18 dexterity would have a +2 to-hit (missile), i.e. his THAC0 (for missile attacks) would be reduced by 2.
  • THAC0 modifiers due to class/level: AD&D rules indicate the following THAC0 modifiers based on character Class and Level.
Class vs. Level
1 2 3 4 5 6 7 8 9
Priest 20 20 20 18 18 18 16 16 16
Rogue 20 20 19 19 18 18 17 17 16
Warrior 20 19 18 17 16 15 14 13 12
Wizard 20 20 20 19 19 19 18 18 18
  • Other: There are also spells and potions that can improve THAC0.

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