Episode 4 was all about using the rules as intended, but yet, not. So what was true in this episode? As you might guess it was the battle with Ghramm’Pahzz, specifically how he was killed.
Once again, this happened to me while I was GMing, but not in my early days. This occurred in the midst of a long-running campaign with an old group. One of my players (my friend Shayne, who actually created the half-ogre barbarian, Bobby, though this was not his PC at the time) used exactly that interpretation of the rules of concealment to slay a wizard they were fighting. We were using 3rd edition rules.
As the GM, my hope was to have a somewhat epic battle, with the wizard eventually falling to the group. He wasn’t even the “big bad” of the campaign, but a powerful lackey. After casting Mirror Image as a delaying action, Shane’s PC stepped forward, closed his eyes and attacked the square.
And there I was faced with that decision: Do I overrule Shayne’s successful use of the rules, so the fight can continue and fulfill my desires for an epic fight, or do I let Shane have his moment in the spotlight and get the cool kill, albeit a little earlier than expected?
Begrudgingly (at the time) I let Shayne have his win, and we moved on. Looking back at it now though, if the situation were to come around again, I would do the same thing, without hesitation.
To paraphrase Star Wars, “Let the players win.” As a GM, you have an unlimited supply of bad guys and opportunities to get your own satisfaction from the game. Take advantage of it.