[quote=@GreivousKhan]
<Snipped quote by Rilla>

It's actually T1 rules for prep includes you should have an [i]'imaginative description of this process'[/i] so it is clear you are doing a prep of some kind. 
[/quote]

Yeah, that is more for the players benefit, still I feel like it's only sporting to give your opponent -the chance- to avoid something because they know its going to be dangerous. It's like the first idea I had when seeing Arena, I was pretty much convinced I could beat the majority of people by using a sword that is actually twice the length it seems to be, but the end is invisible and impossible to detect without investing time and energy analyzing the sword, which no one would do without meta-gaming. That would essentially allow you to stab someone from twice the range they think you can, with no realistic way for them to defend themselves unless they for some reason expect to be stabbed by a sword when it's clearly out of range.

Subterfuge powers really aren't what the Arena is about, the Arena is about duelling in a gladiatorial sense in my opinion, because with the limitless scope of magic you could easily defeat any opponent by exploiting what they can't know about your abilities.