The defender has a -2 to defenses and loses his Dexterity bonus to AC (for being effectively blinded by total darkness), but the attacker has a crippling 50% miss chance because his target is in total darkness (concealment).

The only remaining thing to decide, then, is whether the attacker gets the +2 to attack rolls granted by invisibility. Note that invisibility also prevents opponents from gaining Dex to AC, but this is already covered by the Blind condition).

Personally, I would rule against giving the attacker the +2 to hit. Invisibility is, in my opinion, attempting to mimic the effects of being blind to a single target (that is, the attacker doesn't have +2 to hit, the defender has -2 to AC versus the attacker, but this is easier tracked as a bonus to the attacker's roll than a penalty to the defender's AC). Note that the defender's AC is already drastically decreased by the darkness, and the attacker's main issue in many cases is going to be beating the concealment miss chance, so whichever way you rule on this shouldn't matter too much.

The short answers are Get darkvision!, Turn on the freakin' lights!ou Move away at half speed! because the game makes it very hard to play a

Combat in Darkness

Enquanto um esmagador number of factors pode influence the effects of darkness on the characters below, todos of those myriad factors não pode be covered by this summary. This summary, then, is deliberadamente the game at its most basic, ignoring tudo que pode possivelmente minimize, mitigate, or modify the effects below. I know it doesn't olhar like it, but it is.

A Situação
For ease of use, consider A e B human level 1 commoners who each took the feat Toughness twice so they can survive a round of combat or two contra house cats, instead of, like, serious specialists in night-fighting or something. Also, A e B são o apenas combatants and apenas battling each other--additional combatants on ou side make this already difficult-to-quantify engagement impossibly complex.

1. E se A e B are in the darkness and neither can see through it...

• Ambos A e B suffer -2 penalties to their Armor Classes.
• Ambos A e B lose their Dexterity bonuses (if any) to Armor Classes.
• Ambos A e B move at half speed.
• Nem A nem B can charge or run.
• Ambos A e B suffer -4 penalties to Search skill checks and most Strength-based and Dexterity-based skill checks.¹
• Ambos A e B fail if they attempt any checks or activities that rely on sight.
• Ambos A e B are immune to gaze attacks.
• Ambos A e B fazer todos attacks with a 50% miss chance due to concealment.

• Ambos A e B, as free actions on their respective turns, make Listen skill checks (DC = the other's Move Silently skill check result). Success indicates general direction to the other.² Success by 20 higher than the DC pinpoints the other's location.

  • If either A or B makes attacks sem pinpointing the other's location...

    • each melee attack is made into a acaso square within the attacker's reach.
    • each ranged attack is made in a acaso direction at the closest target in that direction.

  • Ou A or B can, as a standard action, make a touch attack with hands or weapons into two adjacent squares.³ Success pinpoints the other's location if the other is in either square. If the other moves to a different location, the new location must be pinpointed.

• If either A or B is hit by the other's attack, the defensor pinpoints the attacker's location. If the attacker has more than 5 ft. reach or the attack was a ranged attack, the defender knows only the attacker's general direction.

• Nem A nem B can make attacks of opportunity.
• Nem A nem B inflicts precision damage.
• Nem A nem B can use gaze attacks.

Observação: Identical rules are used when both combatants are blind.

2. E se A e B are in the darkness, and A pode see through it, but B não pode see through it...

• A gains no bonuses and suffers no penalties.
• B suffers a -2 penalty to his Armor Class.
• B loses his Dexterity bonus (if any) to Armor Class.
• B moves at half speed.
• B can't charge or run.
• B suffers a -4 penalty to Search skill checks and most Strength-based and Dexterity-based skill checks.¹
• B fails if he attempts any checks or activities that rely on sight.
• B is immune to gaze attacks.
• B faz todos attacks with a 50% miss chance due to concealment.

• B, as free action on his turn, makes a Listen skill check (DC = A's Move Silently skill check result). Success indicates A's general direction.² Success by 20 higher than the DC pinpoints A's location.

  • If B makes attacks sem pinpointing A's location...

    • each melee attack is made into a acaso square within Balcance.
    • each ranged attack is made in a acaso direction at the closest target in that direction.

  • B can, as a standard action, make a touch attack with hands or weapons into two adjacent squares.³ Success pinpoints A's location if A's in either square. If A moves to a different location, A's location again must be pinpointed.

• If B is hit by A's attack, B aponta A's location. If A has more than 5 ft. reach or the attack was a ranged attack, B knows only A's general direction.

• B can't make attacks of opportunity.
• B doesn't inflict precision damage.
• B can't make gaze attacks.

Observação: Identical rules are used when A can see and B is blind. Also, identical rules are used when A is lado de fora of an area of darkness through which he pode see and B is dentro an area of darkness through which he não pode ver.

3. E se A is in the darkness and pode see through it, and B não é in the darkness and não pode see through It...

• A gains no bonuses and suffers no penalties.
• B can't attack A but, instead, picks a square which he believes A occupies and attacks that square's occupant (if any). Due to concealment, attacks contra the square's occupant (if any) have a 50% miss chance.
• B can't make attacks of opportunity contra A
• B doesn't inflict precision damage contra A.

Observação: Porque A não é "blinded by the darkness," A can still make gaze attacks. Because B isn't "blinded by the darkness" B is still vulnerable to gaze attacks. Whether A can use gaze attacks versus B is the DM's call--although technically B should be vulnerable to A's gaze attack (were A to have one), narratively B deveria provavelmente ser imune a A's gaze attack as the darkness in which A resides prevents B from seeing A.

House Rule: Although he's not "blinded by the darkness" the DM may allow a B, as free action on his turn, to make a Listen skill check (DC = A's Move Silently skill check result). Success indicates general direction to the A.² Success by 20 higher than the DC pinpoints the A's location. My opinion is that there should be no mechanical vantagem to blindness--a means to pinpoint an foe's square should be available without having to gouge out one's eyes.

4. E se A is in the darkness and não pode see through it, and B não é in the darkness and não pode see through it...

• A suffers a -2 penalty to his Armor Class.
• A loses his Dexterity bonus (if any) to Armor Class.
• A moves at half speed.
• A can't run or charge.
• A suffers a -4 penalty to Search skill checks and most Strength-based and Dexterity-based skill checks.¹
• A fails if he attempts any checks or activities that rely on sight.
• A is immune to gaze attacks.
• Ambos A e B fazer todos attacks with a 50% miss chance due to concealment.

• A, as free action on his turn, makes a Listen skill checks (DC = B's Move Silently skill check result). Success indicates B's general direction.² Success by 20 higher than the DC pinpoints B's location.

  • If A makes attacks sem pinpointing B's location...

    • each melee attack is made into a acaso square within Aalcance.
    • each ranged attack is made in a acaso direction at the closest target in that direction.

  • A can, as a standard action, make a touch attack with hands or weapons into two adjacent squares.³ Success pinpoints B's location if B's in either square. If B moves to a different location, B's location again must be pinpointed.

• If A is hit by B's attack, A aponta B's location. If B has more than 5 ft. reach or the attack was a ranged attack, A knows only B's general direction.

• Nem A nem B can make attacks of opportunity.
• Nem A nem B inflicts precision damage.
• A can't make gaze attacks.
• B can't attack A but, instead, picks a square which he believes A occupies and attacks that square's occupant (if any). Due to concealment, attacks contra the square's occupant (if any) have a 50% miss chance.

House Rule: Although he's not "blinded by the darkness" the DM may allow a B, as free action on his turn, to make a Listen skill check (DC = A's Move Silently skill check result). Success indicates general direction to the A.² Success by 20 higher than the DC pinpoints the A's location. My opinion is that there should be no mechanical vantagem to blindness--a means to pinpoint an foe's square should be available without having to gouge out one's eyes.

1. Which checks aren't specified but "includ[es] any with an armor check penalty" (DMG 302).
2. The example is "over there somewhere" (DMG 302). This, apparently, ainda doesn't let one choose to make an attack in that direction; random squares and directions remain random.
3. It is unspecified whether this should be separate touch attacks for each square or one touch attack for both squares.

Documentação

All of this compiled straight from the SRD, from the sections on Visão e Luz, which references and summarizes but doesn't actually totalmente detail the condition cego, which, in turn, references and summarizes but doesn't actually totalmente detail the effects of ocultação total. In addition, buried in the Environment section is a treatise on escuridão, which expands on the condition blind and, of course, provides additional rules--specifically, the crazy ones about making random attacks. All of these are taken into account in the cases above.

Check the Treeware!

• The Exploration section on Vision and Light (PH 164-5)
• The Glossary definition of cego (PH 305) and the Condition Summary definition of cego (DMG 300)
• The Combat Modifiers section on Concealment (PH 152-3)
• The Environment section on Darkness (DMG 302)