I'm working on a new build and some questions regarding concealment and the application of this particular stance have come up. I would ask them separately, but it seems to me that all of these are dependent on the interpretation of the same couple sentences of text.
Background: Child of Shadow stance states:
If you move at least 10 feet during your turn, you gain concealment against all melee and ranged attacks until the start of your next turn. You also gain the standard benefits of concealment, but you cannot use this stance to hide in plain sight; you must still use some other terrain feature that normally allows you to use the Hide skill. The fluttering shadows make it difficult to specifically target you, but your enemies are aware of your position.
(Tome of Battle: The Book of Nine Swords, p. 76)
As I understand it, you remain in a martial stance until you declare otherwise; is this a correct assumption?
Let's say a character begins the round already in the Child of Shadow stance. They move 10+ feet and then change stance to Assassin's Stance (a swift action). Assassin's Stance state:
While you are in this stance, you gain the sneak attack ability, if you do not already have it, which deals an extra 2d6 points of damage.
(Tome of Battle: The Book of Nine Swords, p. 75)
Given my current assumptions, the character should now be able to perform a Sneak Attack. Does this sound correct?
Additionally, Child of Shadow does not seem to specify a requirement for the mode of movement; would this imply that any form of movement would apply? Most specifically I wonder about teleportation effects and flight, but I would also wonder about jump, climb, run, etc.
Regardless of sneak attack and mode of travel, does Child of Shadow imply that you continue to maintain concealment from attacks even after attacking?
Finally, and perhaps most subject to interpretation: would an obscure location count for something to aid concealment outside the context of having a tree/bush/cart/etc? An example that comes to mind is a character previously standing in front of an enemy teleports to the ceiling (using spider climb, levitation, etc.); would this be sufficient cause to consider the character hidden enough to perform a sneak attack? I presume even if this is the case, after attacking and without an object to hide behind, any additional hiding effect would be lost (although I do consider some ceilings might be low-light compared to ground level, lighting conditions are outside the scope of my curiosity here). My first thought here was that the enemy would be allowed a spot check, but I wonder what the check would be against? Since there is no hide skill in use, the typical opposed skill check seems out of place?
Edit: To expand on the answer below, it is worth remembering that there is no "facing" in D&D (must be nice to see in all direction at once :P). Just the same as teleporting from "in front of someone" to "behind someone" is impossible, teleporting "above" them doesn't mean they can't see you either.