# How hidden is “Hidden” in Dresden Files

Sally the thief sees guardsman Bob. They are in the same zone, Sally having just rounded the corner. By default, both are aware of each other. If Sally rolls a block using stealth against Bobs Alertness, then the Bob does not see her. On the other hand, Sally could maneuver, trying to place the aspect "Hidden" on Bob. This would let her tag Hidden later, probably for some kind of sneak attack.

I have a Stealth focused character in my campaign. She has been using the first, then the second, in order. Last session, she asked what happens if she skips that first step. My ruling at the time was that she was staying in shadows or otherwise concealing herself, but that the guard knew that somebody was there. She could invoke that aspect to disappear completely from view, representing him losing track of her.

Thinking about it, I'm not sure about this. Should someone who has the aspect "Hidden" be completely unknown? When I have NPCs hiding from players, I tell the players who's hiding from them and usually where they are, and trust the players to stay in character. (It usually works pretty well.) That gets run as a block, and they tend to place the aspect "Concealed" when they're darting around shadows making a hard target of themselves. On the other hand, someone with the aspect "on fire" is still on fire, whether compelled or not- they just don't have any mechanics associated with this. So someone who was "Hidden" could still be unseen.

How should these different versions of hidden be handled?

With the Skill stealth, Sally would already be sneaking around the area, and roll a stealth roll. It would be opposed by the guards Awareness roll. This is defined in the definition of stealth in YS142, and is defined by the rules as a Contest (see YS193).
Block is a combat maneuver, and lasts until the next turn, when a character wants to keep something from happening. The block is the character's action for the exchange, so the character doesn't get to do anything else... even move. See YS210-11 for this.
As far as creating the aspect with a maneuver, that is totally kosher to help with the skill roll. However, I don't think the aspect is necessarily. As you say, it is an absolute- something that is true about the situation. A valid aspect should relate to supplemental actions that would affect the use of the skill, i.e. throw a rock, and the guard might be Distracted by Skittering Sound.
Absolutes are better for situational aspects, such as the On Fire that you quote. When the fire moves to a player, it's better to handle it (depending on the fire) as a Fractal if it's a persistent fire, or just damage if it's not. So, for the situation that you speak of with Sally and the Guard Bob (not to be confused with the Skull), Sally might hex the lights, and the room might be Plunged into darkness.