So I am unsure how darkness interacts with the invisible and blind condition.
Say I have a drow and a human fighting. The Drow casts darkness. What happens?
Possibility 1: Human loses dex and takes -2 to AC. Drow has concealment. From Vision and Light section.
Possibility 2: Like 1 but drow is treated as "Invisible" So also gets +2 to hit. From the Combat modifiers table
Drow has a total of +4 to hit.
Possibility 3: Like 1 and 2, but human is also "blind" so gets a further -2 AC.
Drow has a total of +6 to hit.
Also, when you lose your dex bonus, do you also lose your Shield? Things like darkness and feint specifically say dex bonus, not "Flat-footed" but this seems like a throw-back to 3.5 when you still got shield when flat-footed. If you keep your shield, how do you explain that visually?
As pedantic as it sounds, the drow is not invisible (not under the effects of an invisibility spell effect), so he doesn't get the +2 to hit. Being blind carries the same effects of darkness lowering the light level to a complete darkness for creatures with no darvision (losing Dexterity bonus to AC and taking a -2 AC) and stems from the same source, no light, so the effects wouldn't stack.
When you lose your Dexterity bonus to AC you do not loose your shield bonus to AC. You do however lose any dodge bonus to AC you possess. The AC bonus of the shield still applies because it is still convering a significant portion of the body. Feel free to houserule that you lose some or all of the shield's AC bonus if you lose you Dexterity bonus to AC if it helps with immersion for you, but please tell your players ahead of time that you will be doing so.
The 'vision and light' section repeats the 'blind' penalty from the combat modifiers. The drow isn't invisible, so doesn't get the +2 to hit.
'Blind' doesn't mean 'receives no sensory input from the eyes'. The current legal definition is 20/200 or worse vision, or less than 20 degrees of field of view.
Being in conditions of magical darkness that reduce visual acuity by an order of magnitude constitute blindness. It isn't enough to become invisible.
It depends on the light level. If it goes from normal light to dim light, then it's only concealment and the drow isn't invisible. It's just hard to see. If the Darkness spell causes it to go from dim to complete darkness, then the human is blind. The human loses Dex and the gets the penalty to AC, with the 50% chance to miss when attacking.
And no, when you lose your DEX bonus, you do not lose your shield AC. I'd explain visually as although the target can't see what he's fighting, he's still holding his shield up, now that he knows Darkness is up and something may be approaching.
So if total darkness does not mean invisibility and blindness, does that mean that if the Drow is a sorceress, and casts Blindness on the Human, Invisibility on herself, and darkness on the room, then she will get +6 to hit?
That seems silly somehow.
No. Invisibility is an illusion. Illusions generally do not cause effects on targets that cannot see (with a few exceptions). So there would be no +2 to hit. The loosing Dexterity bonus to AC and taking a -2 to AC are for the same reason; the target cannot see. Bonuses and penalties from the same source, in this case lack of sight, do not stack.
But "lack of sight" is not a condition. The blindness is applied by the Blindness spell, while total darkness is applied by the Darkness spell.
Still, I think what you say makes sense. It seems to me that sight rules are needlessly confusing here. It would be better if there was a line somewhere that said "If the defender can't see the attacker, he gets -2 AC and loses his dex." That would be much easier to understand that mentioning it in 3 places and using different bonuses / penalties.
Thanks Jackalope.
Blinded: The creature cannot see. It takes a –2 penalty to Armor Class, loses its Dexterity bonus to AC (if any), and takes a –4 penalty on most Strength- and Dexterity-based skill checks and on opposed Perception skill checks. All checks and activities that rely on vision (such as reading and Perception checks based on sight) automatically fail. All opponents are considered to have total concealment (50% miss chance) against the blinded character. Blind creatures must make a DC 10 Acrobatics skill check to move faster than half speed. Creatures that fail this check fall prone. Characters who remain blinded for a long time grow accustomed to these drawbacks and can overcome some of them.
Emphasis mine.
The darkness removes the ability to see, granting the blinded condition to a character if it drops the light level to compelete darkness and the character doesn't have another mode of sight (easily removed by leaving the area). The Blindness spell also imposes the blinded condition (somewhat harder to remove). Both penalties stem from from being blinded; they do not stack. The vision and light section is restating the blindness penalties.
No problem.
Still, I think what you say makes sense. It seems to me that sight rules are needlessly confusing here.
You'll find that a lot with the PF rules set, I'm afraid. It has a lot to do with PF being half-copied and pasted and half-new stuff that don't always play nicely together.
Invisibility only gives +2 to hit against sighted opponents. Not sure if this clears things up for you…
http://www.d20pfsrd.com/gamemastering/conditions#TOC-Invisible