I was GMing a PFS table, and one of my players came with a weird rules interaction I couldn't quite wrap my head around. Didn't help that he explained it poorly and he had some of the rules wrong himself. And now, after digging deep into it myself, I'm not sure of it anymore, either. Partially inspired by this old thread, I didn't want to necro that thread anymore, I come to you for help.
The rules interaction is manyfold. First of all, it concerns movement, concealment, low-light vision and so forth (emphasis mine):
Tactical Movement
Tactical movement is used for combat. Characters generally don’t walk during combat, for obvious reasons—they hustle or run instead. A character who moves his speed and takes some action is hustling for about half the round and doing something else the other half.
Hampered Movement: Difficult terrain, obstacles, and can hamper movement (see Table: Hampered Movement for details). When movement is hampered, each square moved into usually counts as two squares, effectively reducing the distance that a character can cover in a move.
If more than one hampering condition applies, multiply all additional costs that apply. This is a specific exception to the normal rule for doubling.
In some situations, your movement may be so hampered that you don’t have sufficient speed even to move 5 feet (1 square). In such a case, you may use a full-round action to move 5 feet (1 square) in any direction, even diagonally. Even though this looks like a 5-foot step, it’s not, and thus it provokes attacks of opportunity normally. (You can’t take advantage of this rule to move through impassable terrain or to move when all movement is prohibited to you.)
You can’t run or charge through any square that would hamper your movement.
Condition Additional Movement Cost
Difficult terrain ×2
Obstacle* ×2
Poor visibility ×2
Impassable —* May require a skill check
So, according to this, poor visibility applies to tactical movement, so during combat, but doesn't give examples of what "poor visibility" could mean. Technically, Obscuring Mist and any kind of area of effect concealment (such as dim light) is poor visibility. This leads me to the next part of this question.
The player also came with the following bit of rules (again, emphasis mine):
Getting Lost
There are many ways to get lost in the wilderness. Following an obvious road, trail, or feature such as a stream or shoreline prevents most from becoming lost, but travelers striking off cross-country might become disoriented—especially in conditions of poor visibility or in difficult terrain.
Poor VisibilityAnytime characters cannot see at least 60 feet due to reduced visibility conditions, they might become lost. , snow, or a downpour might easily lose the ability to see any landmarks not in their immediate vicinity. Similarly, characters traveling at night might be at risk, too, depending on the quality of their light sources, the amount of moonlight, and whether they have darkvision or low-light vision.
This very clearly states that you get lost in mist if you can't see far enough. It is obviously meant for exploration, not for combat, but this is the first (and only) explanation of what fog does on sight and movement I could find. And that also counts for low-light vision and dim light and such.
Sidenote: I also had an Oracle at my table with the Blind curse, and the previous player said his movement was permanently reduced because he couldn't see at least 60 feet ahead. Which, going by these rules is absolutely correct, but instinctively absolutely wrong. Also explained by mtd in the aforementioned link.
So, I still have no idea what exactly the effects of dimness or concealment are on movement. But, on the other hand, the Blinded condition says you need to make a DC 10 Acrobatics check to move at half speed. Following that player's argument, that would stack with the "not being able to see 60 feet" rule, which is plainly ridiculous.
And finally, here's the final piece of confusion: the player used Eclipsed Spell on his Light cantrip to create permanent dim light around him.
Dim Light
In an area of dim light, a character can see somewhat. Creatures within this area have concealment (20% miss chance in combat) from those without darkvision or the ability to see in darkness. A creature within an area of dim light can make a Stealth check to conceal itself. Areas of dim light include outside at night with a moon in the sky, bright starlight, and the area between 20 and 40 feet from a torch.
So, said player wanted to stealth in his own blob of dim light, and claim that because he made his Stealth roll, no one knew he was there, despite the giant blob of darkness around him. Moreover, he claimed that because of the dim light, everyone without low-light vision or darkvision had to move at half speed in his bubble. All of this technically makes sense according to the rules, but logically this should not be a thing.
I am willing to give him concealment, but he claims that everyone is flat-footed against him because of the dim light. I am less sure of that. Obscuring Mist specifically says creatures far away gain total concealment, but poor visibility and dim light never state anything of the sort.
Can anyone illuminate (pun very much intended) me on the subject? I've heard from other GMs that this player tends to interpret/bend rules to his favour, and I'd like to be clear on the subject (mainly, movement in obscured vision, stealthing in his own concealment, and line of sight in low-light vision). Mainly because I now don't trust myself anymore, either.
So, said player wanted to stealth in his own blob of dim light, and claim that because he made his Stealth roll, no one knew he was there, despite the giant blob of darkness around him.
This is correct; the observers would only see the blob of darkness, not the person concealed inside of it.
Moreover, he claimed that because of the dim light, everyone without low-light vision or darkvision had to move at half speed in his bubble.
Dim light is not enough to cause reduced movement speed. You need actual darkness for that.
I am willing to give him concealment, but he claims that everyone is flat-footed against him because of the dim light.
So long as he is hidden by stealth they would be flat-footed against him because they do not perceive him. Once he breaks stealth they are no longer flat-footed. Concealment on its own does not make enemies flat-footed towards you.
First off, getting lost in overland travel has nothing to do with tactical combat at all. Throw away that section as far as this question.
As far as I know, the poor visibility is still undefined. As you noted though blinded makes you move half speed UNLESS you make a DC 10 acrobatics check, so it is reasonable that this 'poor visibility' they speak of is significantly worse than dim light. The GM is the only ruling on whether something does or does not count as poor visibility (and it would probably be a special environmental hazard, not just darkness). I could see it for a volcano spewing clouds of ash or something, or wading through murky water maybe. Anyway, it would be built into an encounter. I don't know of any spell or magic item that specifically creates a 'poor visibility' environment, or even one that notes similar penalties based on reduced vision (except of course for blinded).
Lastly, and eclipsed light spell would create an area of dim light under normal lighting conditions. Under bright lighting conditions (like outside in the sun) it would just create normal light.
If a character has concealment, they can stealth. That doesn't cover up illumination areas they are in. The area of dimness would be quite visible to everyone, even if they didn't perceive an individual inside that dimness. This is also true of invisibility where it talks about light sources directly if you want more backup. Also stealth is an opposed roll, stealth vs. perception so there isn't a 'making it' exactly.
If they successfully stealth they can achieve an ambush (act in the surprise round and maybe act before their opponents) and their opponents will be flat footed until they act. Other than that, their opponents being unaware of them would lose their dex bonus to AC (similar, but not quite flat footed) but this ends after 1 attack roll and would typically require movement to gain it back, so during a combat they could make one attack per round in this manner.
Lastly, this is pretty easy to counter. Besides low light and darkvision killing it, only the highest level light spell applies in a given area, so a simple continual flame (ever-burning torch) is going to strip away his concealment.
no stealthing in the open just because of dim light
This is untrue; you need cover or concealment to use stealth. If the lighting conditions are poor enough to give you concealment, you can use stealth.
First off, getting lost in overland travel has nothing to do with tactical combat at all. Throw away that section as far as this question.
I missed that one. Yes, getting lost applies to exploration. Most fog and darkness effects are not large enough to get lost in.
You do not need total concealment or total cover to use Stealth. Concealment is sufficient, as is cover, so long as you aren't being observed. The entire point of Stealth is that successfully using it means that creatures treat you as if you had total concealment. If you had to already have total concealment to use Stealth, it wouldn't be very useful.
You cannot use Stealth if you are being directly observed, though, unless you have an ability that states otherwise (such as hide in plain sight) or succeed at a Bluff check. If you are in the middle of combat and the combatants are aware of you, you probably won't be able to use Stealth simply from being in dim light--not because you don't have enough concealment but because combatants are assumed to be directly observing any other combatants that they are aware of. A Bluff check would be needed here.
Rules points have been answered by others above, the below is simply my opinion, and not the actual rules.
Honestly the limited (and undetailed) rules clash with the rules for being blind. Being blind means to make a DC 10 acro roll or move at half speed. Having poor visibility just means move at half speed with no option for an acro roll. So poor visibility is somehow a worse condition than being completely blind? Worst case it should be treated the same as blindness, a better case would be for the GM to give appropriate bonuses to the acro roll depending on just how poor the visibility is. e.g, Total darkness, no different than blind, heavy smoke or fog, say +3 to the roll, light smoke or fog +5 or more - or whatever the GM feels is appropriate.