Attacking

When a character has spent an action and an attack to strike out at a foe, they are said to be Attacking.

To-Hit

At the heart of attacking is the character's ability to hit their foe. To determine this, the character must know one thing immediately - their character's THAC0. This stands for To-Hit Armour Class 0, or the number that Character would need to hit someone with AC 0. A character with THAC0 20 needs to roll 20 to hit AC 0, a character with THAC0 10 needs to only roll 10! A lower THAC0 is better as it means the character needs to roll a lower number on the dice itself to successfully hit.

To-Hit Roll

The To-Hit Roll is defined by a straightforward formula - it seems awkward at first due to the fact that AC counts down from 10 by default, but people get used to it.

To determine what AC the character can hit with their attack, roll the following:

thac0 - 1d20 - To-Hit Bonuses + To-Hit Penalties.

Effective thac0

To simplify this matter, a player can quickly adjust their Effective THAC0 and then roll something based on that. This is simplified significantly by using Dice Macro.

For example, a character has a thac0 of 14 and is wielding a +1 Longbow against an enemy who is behind 50% cover (-4 to hit). This means that the To-Hit Roll looks something like this:

14 - 1d20 - 1 + 4

Which simplifies down to:

17 - 1d20.

In short, they have an effective THAC0 of 17.

Making The Roll

When the dice is rolled, if the To-Hit roll comes up with the AC of the target or lower the attack is a hit! To continue the above example, the character with the effective THAC0 of 17 rolls 11, this gives them a To-Hit Roll of 6!

If the target has AC 6 or worse, that'd be a hit! If the target has AC 5 or lower, however, that would miss! Say the target has AC 5 - in their current position they'd need to roll 12 or better to hit the target. On a d20, 12 or more is only a 45% chance. If they move to a place where they are behind the target, they lose the -4 penalty and gain a +2 for a back attack. Their effective THAC0 of 17 becomes 11! Now to hit the target, all they need is 6 or more! Their chance to hit when up from 45% to 75%!

Results

If the attack misses, nothing happens - usually. In the case of enormous throwing weapons or grenades, the location where the projectile does land is often important.

If the attack hits, the character may roll Damage.

If a 1 or 20 is rolled, it may be considered a Critical, Critical Hit or Fumble

Modifiers

There are many situations and conditions that can modify the ability of an attack to hit.

Enhancement

Enhancement refers to a bonus or penalty tied to the weapon itself, effectively unchangable. This is usually magical but it could be technological or otherwise.

A Weapon will almost always have Enhancement (To-Hit) and Enhancement (Damage) of equal value; if it is a +1 Weapon, assume it does unless stated otherwise.

An Enhancement modifier applies to both To-Hit and Damage - these do not normally stack and only the highest Enhancement modifier is considered.

The only exception comes when using Ranged Weapons and Ammunition - the Enhancement modifier of ammunition and ranged weapons stack; thus a +1 Longbow firing +2 Arrows has a +3 To-Hit bonus. If the character has an Enhancement modifier from other items, it is only considered for Ranged attacks if it is higher than the Ranged Weapon's Enhancement, not the Ammunition.

When determining the ability to penetrate Special Defence, the highest Enhancement Modifier across ranged weapon and ammunition is used in Heroic and Epic games. In Traditional Games, only the Enhancement modifier of the ammunition is considered.

If Magical Ammunition is retrieved after successfully hitting a target, its Enhancement bonus decreases by 1, until it becomes 0. Some Ammunition lose all Enhancement bonus immediately on a successful hit. Enhancement penalties are not lost or gained in this manner.

Circumstantial Modifiers

Unless specifically stated otherwise, To-Hit modifiers are considered Circumstantial. They may be listed on a Stats Sheet as from Strength or Dexterity but they are circumstantial and, unless obviously unable to interact, they stack.

The table below lists a large number of standard To-Hit modifiers that may come up in play, based on the circumstances characters find themselves in. Modifiers that come from attributes, specializations, conditions and so forth are generally not listed here.

Some modifiers stack - a prone target attacking with a crossbow who is able to fire at a target below them has a +5 To-Hit bonus. Other modifiers replace each other - an attacker who is climbing does not gain a +1 bonus To-Hit from being above their opponent, nor does an attacker in Visibility 25% suffer both the penalty for Visibility 25% and Visibility 50% at the same time. A DM decides if multiple modifiers stack or not.

Circumstantial Modifiers
Relative Position	Modifier
Attacker is Above Target	+1
Attacker is Climbing and is Above Target	+0
Attacker is At Same Level as Target	+0
Attacker is Climbing and is At Same Level as Target	-2
Attacker is Below Target	-1
Attacker is Climbing and is Below Target	-4
Prone Stance	Modifier
Attacker is Prone and Attacking with Melee/Throwing Weapon (Size < Attacker Size)	+0
Attacker is Prone and Attacking with Melee/Throwing Weapon (Size = Attacker Size)	-2
Attacker is Prone and Attacking with Melee/Throwing Weapon (Size > Attacker Size)	-4
Attacker is Prone and Attacking with Ranged Weapon (Gun-like - Gun, Crossbow, Blowgun)	+4
Attacker is Prone and Attacking with Ranged Weapon (Other - Bow, Sling)	-4
Target is Prone (Melee Attack)	+4
Target is Prone (Ranged Attack within 10 or less feet)	+0
Target is Prone (Ranged Attack > 10 feet away)	-2
Kneeling Stance	Modifier
Attacker is Kneeling/Sitting and Attacking with Melee or Throwing Weapon	+0
Attacker is Kneeling/Sitting and Attacking with Ranged Weapon (Gun-like - Gun, Crossbow, Blowgun)	+2
Attacker is Kneeling/Sitting and Attacking with Ranged (Other)	+0
Target is Kneeling/Sitting (Melee Attack)	+2
Target is Kneeling/Sitting (Ranged Attack within 10 or less feet)	+0
Target is Kneeling/Sitting (Ranged Attack > 10 feet away)	-1
Balance	Modifier
Attacker is Off-Balance	-2
Target is Off-Balance	+2
Attacker is Off-Balance on Narrow Platform (Tightrope Walking)	-5
Target is Off-Balance on Narrow Platform (Tightrope Walking)	+5
Underwater	Modifier
Attacker is Underwater and does not have a Swim Speed	-2
Target is Underwater and does not have a Swim Speed	+2
Attacker is Underwater (Piercing Melee Weapon or Net)	+0
Attacker is Underwater (Other Weapon)	-4
Attacker is Wading, Target Underwater (Piercing Melee Weapon or Net)	-2
Attacker is Wading, Target Underwater (Other Weapon)	-6
Visibility	Modifier
Target has 25% Cover	-1
Target has 50% Cover	-2
Target has 75% Cover	-4
Target has 90%+ Cover	-6
100% Visibility (Sunlight)	+0
75% Visibility (Moonlight)	-1
50% Visibility (Starlight)	-2
25% Visibility (Clouded Night)	-3
0% Visibility (Total Darkness)	-4
Per 10 feet between Attacker and Target at 0% Visibility	-1
Range	Modifier
Short Range	+0
Medium Range	-2
Long Range	-5
Extreme Range	-10
Weather	Modifier
pending	pending
Condition	Modifier
Attacker is using Off-Hand	-2
Target is Invisible	-4
Target is Stunned	+4
Precision Attack (avoiding Firing Into Melee)	-4
Flanking (per Outnumbered)	+1
Back Attack	+2, Flatfooted
Sneak Attack	+2, Flatfooted
Target is Unaware, Surprised or Ambushed	+1, Flatfooted
Target is Helpless (Melee Attack)	+10, Flat Footed
Target is Helpless (Ranged Attack)	+5, Flat Footed