Glamours don't cost mental stress if you look in the raw any power that requires mental stress says that it requires mental stress, if glamours worked on the system of mental stress there would be an option to incease the strength of the glamour by using more stress.
I disagree. I believe Glamours does not cause mental stress.
For one thing, if Glamours worked like Evocation, then you have to have Conviction to determine the stress, and roll Discipline to control it. The Glamours entry mentions neither. With Evocation veils, the power you call up determines the stress level and block strength, but with Glamours, Deceit or Discipline determine block strength. This is clearly a different mechanic. If you ran it like Evocation, then how many shifts of power would you require the player to call up? One? Zero? But there's no benefit to calling up more.
Since Glamours is limited to stealth and trickery, I do not see it as needing the balance of limited uses per scene as Evocation does. Adding mental stress to Glamours is needlessly complicating a story-oriented power by adding combat trappings and implications.
Though, after reading through replies, as the GM in this case I've made a decision. I think I will remove the mental stress requirement from the power. I will simply have to do some serious consideration on combat uses.
If it is going to be used in combat to make someone "poof" in the middle of a fight?
Given that it is only allowed to "pure fae of considerable power" I think this is one of those things that was never really intended to be used by PCs in the normal course of affairs. It is more of a model than a carefully balanced power.
Why didn't you just let him take regular glamours or did he not want too. I think if people wanted a stronger glamours power in one of my games I would let them get the +2 to veils and seemings without true seemings for +3 refresh instead of 4.