Quote Originally Posted by Hal View Post
For the curious . . .
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My players infiltrated an enemy fortress disguised as the enemy's elite guards. However, their ruse was blown instantly because the elite troops use special magic equipment that the players couldn't replicate, and they were recognized as phonies. This led to combat in which the players were victorious.

My questions in this case: Did the recognition that they were fakes cause someone to see through the illusion? Did the combat cause the illusion to vanish? One of the PCs has a glass eye, or in this case, he's a dwarf with a giant emerald eye. Was that visible through the illusion? The enemy is going to be using "Speak with Dead" on the killed troops, they'll want to know who was responsible.
No, a giant glass eye would not be instantly detectable through the illusion. As Kurald said, the illusion would "break" after about 5 minutes, although note that there is no daily limit on the number of times the Hat of Illusion can be used; you could just reactivate it. It wouldn't be inappropriate to rule that the disguise (unless broken magically) still continues until the players deactivate it).

Technically, all that's needed is an excuse to "break" the illusion. I'm going to assume you just ruled that their illusion was "broken" but didn't actually have an idea how? Here's a few suggestions to "cover" your butt (although in the future, I would reward their creativity):

  • A single enemy (perhaps a BBEG) with a high enough passive perception, who signaled the rest
  • Some secret call sign/action which the guards would know, but the PCs did not (allowing for active perception/insight checks).
  • Perhaps some magic ritual (make it obtainable from the PCs) grants people the ability to detect illusions. For example, the level 11 ritual "Banish Illusions" (Eberron Player's Guide)