Combat Rules

One turn is equal to 10 minutes, and equal to 10 rounds.
One round is equal to 1 minute, and equal to 10 segments.
One segment is equal to 6 seconds. 1 segment is also equal to 1 "point" of initiative. The time between initiative 3 and 4 is 6 seconds.
In combat, all rounds are approximate and can last anywhere from 20 to 60 seconds.

Surprise

Before combat begins, surprise may be rolled. Surprise is rolled for one or both parties if one or both of them were not expecting/aware of the other party. To check surprise, a d10 is rolled - for a normal human, a roll of a 1-3 indicates surprise, while other races and creatures can vary. If anyone is surprised, then a "surprise round" occurs before the combat proper begins. During the surprise round, anyone who is not surprised may take a full round of actions; spells can be started in the surprise round, but will finish during normal initiative. During the surprise round, surprised creatures get no bonuses to AC from DEX, and their attackers get a +1 bonus to hit them.

Although most creatures are surprised on a roll of a 1-3, there are specific modifiers that alter this:

Other party Modifier to Surprise Roll
Silence -2
Invisibility -2
Strong stench +2
Each 10 members +1
Camouflage -1 to -3
Your party Modifier to Surprise Roll
Fleeing -2
Suspicious/Anticipating attack +2
Reaction adjustment Variable
Other modifiers Modifier to Surprise Roll
Poor light -1
Darkness -4
Rain -1
Fog -2
Very still conditions +2

Ambush

Ambushes are different from surprise: an ambush is a premeditated, concealed attack which is prepared beforehand - your are laying in wait for an enemy. Depending on how well the ambush is prepared, the ambush may fail - if so, the enemy still has to roll for surprise (as you have surprised) them, but it does not count as a full ambush. If it passes, however, you get a free round of attacks AND your enemies then roll for surprise normally, meaning that a successful ambush could get two free rounds of attacks on their enemies. Unlike during a surprise round, an ambushing spellcaster CAN cast spells. There is no roll for an ambush - either it's successful, and you get the ambush AND roll surprise, or it's unsuccessful and you just roll surprise. Just as during a surprise round, ambushers get a +1 to-hit and ignore DEX bonuses to AC.

Sneaking

Surprise rolls are also used for sneaking as it pertains to non-thieves. Obviously, in many cases, sneaking is simply impossible: you cannot even attempt to move silently if you are wearing heavy armor. Even if you are not wearing heavy armor, youe chances of success are much lower, and you will never be able to perform the same feats that a thief can with Move Silently. If you are aware of someone but want to sneak up to them or around them instead of surprising them, roll surprise for the enemy. If they would normally be surprised, instead they are unaware of you. They will remain unaware of you either until you do something that would reveal you (such as coming within 20 feet of them or entering a well-lit area), or until 1 turn is passed, at which point they most roll for surprise again. Obviously, if their roll indicates that they are not surprised, then they are both aware of you and unsurprised. Note that if you are sneaking in this manner and you are going to try to do something that would require Move Silently - such as sneaking directly up behind a guard to backstab him - you will use the minimum base Move Silently score of thief, plus any armor, dexterity and racial adjustments. Needless to say, this is unlikely to succeed; the base score for Move Silently is only 10%.

Initiative

At the beginning of each round, each player rolls 1d10 to determine their initiative. Each enemy or group of enemies rolls a 1d10 as well to determine their own initiative. Running through initiative order, each player declares movement and actions. Actions with a speed - such as attacking with a weapon, spellcasting or activating a magical spell - create a modified initiative. A fighter who rolls a 4 and fights with a dagger moves on 4 and strikes on 6. A wizard who begins casting Sleep on 3 finishes at 4.

If a player beats a spellcaster's initiative, they might decide to hold their action until the spellcaster begins casting to try and interrupt them. This is possible; but the casting time and weapon speed should be kept in mind. For example, Magic Missile has a casting time of 1; even if you wait until the caster begins their spell, you can't throw a dagger (speed 2) fast enough to interrupt them.

You can take one significant action per round, such as taking out & drinking a potion, attacking, moving up to your speed, casting a spell, etc. If you move one-half or less of your speed (usually 60') you may also make your attack. You may move up to 1/2 of your speed and make an attack with a missile weapon, but only at 1/2 of your normal rate of fire.

Special Abilities

Some items and abilities act as if they were spells. These are listed here, along with their "casting time".

Breath Weapon = 1
Natural or Spell-like Ability = 3
Miscellaneous Magical Item = 3
Potion = 4
Ring = 3
Rod = 1
Scroll = casting time of spell
Stave = 2
Wand = 3

Natural spell-like abilities can be used at the same time as spellcasting or fighting if you have an Intelligence of 16 or more.

Other Modifiers

Haste = -2
Slow = +2
High Ground = -1
Set to Receive a Charge = -2
Bad Footing or Conditions = +2
Wading in Deep Water or Limited Mobility = +4

If you are fighting unarmed, your weapon speed is 1. If a creature is fighting with natural weapons such as claws or teeth, their weapon speed depends on their size. If there is another listed weapon speed for the natural weapon, use that instead.

Tiny = 0
Small = 3
Medium = 3
Large = 6
Huge = 9
Gargantuan = 12

Movement

Every character has a speed value - humans have a speed of 12 when unencumbered, for example. When in the dungeon, in combat or in some other situation where you are being careful and watching your step, you move ten times this value in feet per round - so a human moves 120 feet. If you are being careless or travelling overland, you move three times as fast - so a human moves 360 feet. If you choose to move at your full speed when in a dungeon or similar setting, but you get a -1 to your surprise rolls and enemies get a +1 to theirs, and you also will not notice traps, secret doors or other hidden things. You are also deprived of Dexterity bonuses to initiative, surprise rolls and AC. If you move past an enemy in combat at this speed, they are entitled to a free attack.

You may also charge at your full speed (i.e. 360 feet for a human) and make an attack, getting a +2 bonus to-hit. When charging, regardless of weapon speed, you will always strike before your enemy unless they are guarding or set to receive it. However, charging increases your initiative score by 2 each time. For the rest of the round that you charged on, you also gain no DEX bonuses to AC, and your AC is further reduced by 1. If you are guarding (or "set to receive a charge"), you automatically attack first against anyone who engages you, unless they are charging. If they are charging and you are guarding, the person with a longer weapon reach strikes first. If you are set to receive a charge with spears or pikes, you deal double damage on a successful hit. Charging past someone within the reach of their weapons will provoke free attacks from them.

When moving out of combat, you can either withdraw or flee. If you flee, you simply move away from the opponent, but he gets a free attack against you when doing so. If you withdraw, he does not get this free attack, but you may only move up to 1/3rd your normal speed and may take no other action that round. Any action that ignores an enemy who is capable of hitting you provokes an attack of oppurtunity, but only one such attack can ever be taken by a single creature in their round.

Running & Chasing

Jogging or running increases the speed moved to a maximum of sixty times the speed rating - so with a speed of 12, one can run 720 feet in a round. Running in combat reduces your AC by 4 and entitles any you pass by to a free attack on you.

For dealing with situations where one is being chased by another, use the rules found on the pursuit page

Attacking

When making an attack roll, roll a d20 and compare the result to your THAC0. If your THAC0 is 20, you need a 20 to hit AC 0, a 19 to hit AC 1, and so on. As a shortcut, subtract the enemy's AC from your THAC0 to get the number you need to roll to hit them.

You may dual wield melee weapons, so long as the weapon in your off-hand is lighter than the weapon in your main hand. You get a -2 penalty to hit with your main hand, and a -4 penalty to hit with your off-hand. Both of these are reduced by your reaction adjustment, to a minimum of -0/-0. If you try to dual-wield with two weapons of equal size, you get a -4 penalty to hit with your main hand and a -8 penalty to hit with your off-hand. Taking a proficiency in Two-Weapon Fighting reduces the normal penalties to -0/-2. Specialising in Two-Weapon Fighting allows you to use two weapons of equal size at -0/-2. Daggers and knives always count as secondary weapons, so you can always wield two daggers without additional penalties.

When attacking an enemy who is unarmed, completely distracted (i.e. casting a spell), or wielding a ranged weapons, you get a +4 bonus to-hit. If you hit a spellcaster while they are casting a spell, you disrupt the spell. If you hit someone who is wielding a bow or crossbow, there is a 50% chance their weapon is damaged or destroyed.

When attacking from the rear you get a +2 bonus to-hit and negate DEX and shield bonuses to AC. Backstabbing thieves get the same bonuses, but the bonus to hit is +4 rather than +2. Unconscious or helpless enemies are critted automatically in combat. Outside of combat, unconscious or helpless enemies can be killed instantly.

Concealment is expressed as a penalty to-hit, while cover is expressed as a percentage chance to miss; these only apply to ranged weapons, of course. For example, hiding in a dense bush might provide a -2 penalty to hit, while a low wall that blocks half your body provides 50% cover.

Situation Combat Modifier
Prone enemy (melee) +4
Prone enemy (ranged) -2
Off-balance enemy +2
High ground +1
Invisible enemy -4
Surprised enemy +1

Sweeping

Warriors (fighters, rangers and paladins) get extra attacks when fighting enemies with less than 1 HD (kobolds, rats, goblins etc). Against these types of enemies they can make a number of melee attacks per round equal to their level. They get the same number of attacks against anything with 10 or more HD less than them - so an 12th level fighter could take 12 attacks per round against 2 HD enemies, for example.

Note that there is a limit of one attack per creature when sweeping: a 15th level fighter can't choose to hit a 5th level fighter 15 times.

Firing Into Combat

Firing into melee is always a dangerous proposition - unless the archer is extremely skilled, they are just as likely to hit a friend as a foe. When an archer fires into combat, the DM simply assigns all creatures of equal size an equal weighting, and rolls to see which is hit. A small creature in a battle against a medium creature would only count for 1/2, a large creature counts for 2, and so on.

If you are specialised in a ranged weapon, you may take a -4 penalty to-hit in order to fire safely into combat. For specialists, this can only be done if the combatants are not fighting at closer quarters than short swords. Weapon Masters may increase this penalty to -6 to safely fire at all those who are not grappling. High Masters may increase the penalty to -8 to even be able to fire safely into a grapple.

Death & Fatigue

Any character who falls to 0 hp falls unconscious, and a normal (0-level) person dies at -1 hit points. A character has a number of negative HPs beyond the basic -1 equal to their level - a 4th level has up to -5 hit points before they die, and so on. Going below 0 hp requires a saving throw vs. death to avoid serious disfigurement and coincident stat loss - usually CON/DEX/CHA, but possibly STR/INT/WIS as well. The amount lost is usually between 1 and 3 points, though serious injuries may aggravate this while gradual injuries may reduce this.

Tired characters are less effective in combat. 8 hours of sleep are needed to rest the body and mind, and to allow magic-users to replenish their spells. Fatigue sets in after 16 hours of light activity - or 20 with the Endurance NWP. Combat and exertion will cause you to fatigue faster - 1 minutes of exertion is equivalent to 10 minutes of light activity. Fatigued characters receive a -2 or 10% penalty to all attack rolls, ability score checks, and all similar tests.

If a fatigued character tries to continue on regardless, they can continue as they are for a number of additional hours equal to half their Constitution score (once again, heavy exertion makes this time pass faster). A character with a Constitution score of 12, for example, can continue in a fatigued state until 22 hours have passed since their last rest. At this point, their condition worsens and they become exhausted. The penalty drops to a -4, and if they do not remain active, they must make a Wisdom check each hour to avoid falling asleep.

If the conditions are active and noisy, such as on horseback or in the midst of a war camp, they only need to make a check every six hours. Obviously, some conditions - i.e. in the middle of a battlefield - will make it impossible to fall asleep, no matter how tired you are. You can stay awake indefinitely in these conditions, but quickly begin to risk insanity.