Here is the idea. Sorry in advance for the wall of text. I'm sure there are holes, but I think it's pretty solid so far. Thoughts?
Being Hidden in Combat
By being hidden, you are essentially preventing an opponent, or anyone else for that matter from gaining information about you. But being hidden can also prevent particular actions, namely attacks and maneuvers against you. Therefore, the effects of being hidden can be broken into two parts. Information and Conflict Actions.
Information:
Being hidden prevents an opponent from gaining information about you. Who you are, what you're doing, how you're doing it.
In dealing with hidden information, set a difficulty based on the environment (lighting, chaos, things to hide amongst, etc.) taking into consideration how much fun things will be for the players. To discover hidden information, roll Investigation or Alertness against the set difficulty at the beginning of your turn. Information is given based on the shifts gained from the roll each round. Obvious information is obvious and shouldn't require a roll to be discovered. (The bullet hole in the wall beside my head tells me I'm being shot at.) However, for information that isn't obvious, each shift gained reveals a small amount of information about the hidden person or thing. (Zone location, weapons used, number of opponents, identity, etc.).
The reason that information is given out slowly rather than all or nothing, is that when you interact with the world around you, you leave your mark on it. Small bits of information that reveal who you are, what you're doing, and how you're doing it. (Cut someone with a sword, and they'll know you are using a sharp melee weapon.) Particular information can be requested by the person, but it is up to the GM whether that information is knowable from the actions the hidden person has taken. Also, larger reveals, such as identity, should require some lead up questions/information before the big information becomes known.
As long as the effect of being hidden is not being used to block Conflict Actions, this effect will remain in place until the block strength is overcome or circumvented, it is dropped purposefully by the person who created it, or the scene ends.
The benefits of being veiled this way are largely tactical in nature. By not knowing where your opponent is, moving around the scene of the conflict to your best advantage becomes tricky. By not knowing what weapons or armor your opponent is using, choosing the right attack is difficult. By not knowing who your opponent is, invoking known aspects is impossible.
What about not being able to see a strike coming from a hidden opponent? Any dodges resulting from a hidden attack is restricted by Alertness. This effect is removed for one round if an Investigation/Alertness check succeeds against the set difficulty. This effect is removed entirely if the block is overcome. This constant penalty to an opponent's defenses makes being hidden a very useful effect in a conflict. Keep in mind that this is balanced in one of two ways. The first is that veils, whether through magic, through glamours, or through any other means, prevent perception both ways as per YS276 (it doesn't specify means other than magic, but I will include them for balance purposes). All actions made through a veil will suffer a penalty unless the 2 additional shifts to make the veil completely transparent are included at creation. This often makes most other blocks more effective at preventing attacks and maneuvers (see below) at least than a veil (though the tactical benefits of hidden information is arguably worth it in some situations). Since mundane stealth suffers no penalties to perception the way veils do, the second way the penalty from hidden attacks is balanced is through the difficulty to remain hidden by mundane means (see Mundane Stealth below). Typically, only snipers can remain hidden and attack for longer than an exchange or two without the use of magic.
Conflict Actions:
You can also use being hidden to block all physical attacks and maneuvers against whatever or whomever is hidden. The strength of the block is determined by the power of the veil being cast, the strength of the glamour being created, or a Stealth roll. As with other blocks, if someone wants to land an attack or maneuver, they need to overcome the block. If they do, then 1) the attack or maneuver lands, 2) the block is overcome and is gone, and 3) all information about the hidden becomes public given it makes sense to be public. If they don't, then they missed, and the hidden remains hidden. Blocks of this nature only last for one exchange unless duration is added to the effect. Typically only wizards are able to add duration to a veil cast through evocation. Most others will need to roll every exchange to maintain the block as per the normal blocking rules.
But what about not being able to see where a hidden target is in order to aim your attacks? In essence, that is what the block is. It is removing your ability to aim an attack. If the block is overcome, then you were able to see the target enough to at least land an attack, but if the block holds then you missed, maybe even wildly.
But what if I use a melee attack on a hidden opponent who isn't in the same zone with me? Naturally, your attack won't succeed, but not all will be lost. First you learned that your opponent wasn't in the same zone as you. Second, you gain the option to take that attack and turn it into a maneuver placing an aspect upon yourself related to seeking or searching for use on your next turn, but only if the total shifts of your attack is 3 or greater.
Mundane Stealth:
Disappearing mid-combat by non-magical means is a tricky proposition and should probably require ample justification or a stunt. The same for staying hidden after attacking someone from hiding. The further you are from a target the easier it is to remain hidden, so this will be broken up by distance.
Same Zone:
It is extremely difficult to remain hidden and do anything while in the same zone as an opponent. You must have made a Stealth roll to remain hidden before an opponent has noticed you. You cannot make this roll after an opponent has noticed you without a stunt or strong justification from the environment as well as an aspect being tagged/invoked. Whether you choose to block information only or also choose to block Conflict Actions, the way being hidden is handled does not change . . . with one exception. Once you attack or otherwise physically interact with an opponent, you are automatically revealed and your block is removed. If there is enough justification for it, this effect may be limited only to the person you've interacted with. After you are revealed, you will need an appropriate stunt or strong justification from the environment as well as an aspect being tagged/invoked to reestablish such a block.
Moderate Distance:
Using a ranged attack allows a bit more flexibility in remaining hidden, or disappearing again after being noticed, but not much. As long as you are at least 1 zone away, but still within easy visibility distance, you may take a supplemental action with an attack to duck behind something in order to remain hidden, provided there is something to duck behind. This will still reveal which zone you are in though the rest of your block will remain in place until your next exchange. If you attempt to change zones before reestablishing the block in the next exchange, you will be revealed unless you have an appropriate stunt or an aspect to tag or invoke. The same is true if you are trying to establish another Stealth block after being revealed with fewer justifications needed than if you were in the same zone as your opponent(s).
Long Distance:
Using a very long range weapon, such as a sniper rifle, provides the greatest flexibility in hiding and remaining hidden in conflicts without the use of magic. After an attack is made, your opponents will know which direction the attack came from, but not your exact location. In fact, the Investigation/Alertness checks at the beginning of each round won't start until you are located and the distance to you is reduced. To do this, an Investigation or Alertness roll is required. The difficulty is set by a Stealth roll, plus the number of zones you could be in, plus the 1 for each level of speed powers you possess. Subract the Investigation/Alertness roll from the difficulty and the remainder is how many exchanges it will take to reveal you. If there is no remainder, your location is revealed, but not the information about you. Every attack you make after an Investigation/Alertness roll to find you is made reduces the number of exchanges it will take by 1. Additionally, a searching opponent may move through zones you might be in to reduce the amount of time to find you by 1 exchange per zone. The only way to stop an opponent from locating you is for a concession to be made by either party. Once you are located, an opponent must be within reachable distance of you for the Investigation/Alertness checks to begin revealing information unless they possess some means to see at a long distance. Changing zones will not automatically reveal you, but once your location is revealed an appropriate stunt or an aspect to tag or invoke is required to reestablish the block and begin the locating process over again, provided you are still far enough away to justify it.
