I have never tried it and would never run it unless the players welcomed the idea. But I must stress that there are fundamental differences between my suggestion and Omnusi's experience: in Omnusi's game, the player's reaction was provoked by feeling of being deceived by a player and GM. In my game on the other hand, there is no deception. Either:
A). The players hear a story about how some NPCs were killed by the campaign villain or
B). The players take over the role of those NPCs in their final encounter for a one-shot adventure.
By choosing this second action, the players may lose a session of PC development, but they will gain clearer insight into and appreciation of the strengths (Tactics and intelligence) and weaknesses (Potential flaws) of the campaign villain.
It could only work as part of a long campaign when players' initial obsession with playing and updating their character at every opportunity has waned.
I have only the haziest impression of the rate that PBPs progress but in a tabletop campaign reaching its middle stages, I would play an important NPC for an hour or two if it would offer my PC a good insight into defeating the central villain.
Even monsters that are not particularly intelligent should come up with clever tactics sometimes. Foxes can, so why not goblins or orcs? Only the truly stupid - zombies and stirges, etc - should attack without thought. In my games, most creatures use clever tactics on a successful intelligence check, but if they fail, they just fight or flee.
The irony here is that its not so much about the intelligence of the monster as much as it is about how intelligent the GM is to apply the probable actions of that monster.
Good point Expert. It can also be the opposite. The Dungeon Master makes the monsters too smart and they tend to outwit the party even though they aren't bright enough to do that but honestly I've never encountered that. *crosses fingers*.
If monsters share a pack mentality then they would act according to those natural traits.
If you want to show that a monster is intelligent then determine what his level intellect would translate into for a human. What traits, talents, or characteristics would a human of that intellect do or perform.
Intelligence in most Role-playing Games is scaleable and actions that reflect these scales appropriately would be the best way to demonstrate this in a game.
If a monster escapes and is likely t return in the future, have it show up with some new talents, skills, or traits. Show that it at least learned a small something from it's last encounter with the PCs.
A monster escaping and then returning more powerful sounds like a good vengeance game. I've never encountered that before, except maybe in Super Hero Role-playing Game. Most times we tend to finish them off right away and hunt them down.
A sign of some level of intelligence is knowing when to run. The time away from the PCs to heal, also an intelligent thing to do. Devising a means to attack the PCs, also a sign of intelligence.
How much intelligence would dictate how thotough a plan they have,.