It probably should be noted that I've actually run "The Hall of Harsh Reflections" with the actual Mindflayer Sorcerer 7.
The first combat (against six level 7 PCs, IIRC) was game, set and match to the Mindflayer, with at least two PC deaths.
The second combat had two invisible, flying fighters (alright, a barbarian and a paladin) blindsiding the Mind-flayer as the rest of the party distracted him, and then scoring criticals as he provoked AoOs as he moved closer to the rest of the party... that was a good feeling for the party.
Cheers!
The first combat (against six level 7 PCs, IIRC) was game, set and match to the Mindflayer, with at least two PC deaths.
The second combat had two invisible, flying fighters (alright, a barbarian and a paladin) blindsiding the Mind-flayer as the rest of the party distracted him, and then scoring criticals as he provoked AoOs as he moved closer to the rest of the party... that was a good feeling for the party.
Cheers!