I was just watching some of The Gauntlet videos on Youtube; if you're not familiar, it's a test of high powered builds, to see if they can tackle a nasty solo adventure with the aid of two NPC sidekicks. In the last battle, you have to stop a Mind Flayer Arcanist from finishing a ritual after defeating his goons.
The last video I saw, the player's character died, the Expert NPC died, and the warrior remained...but it was basically over at that point because the Arcanist was protected by a Wall of Force, so even if they miraculously defeated the minions, they couldn't stop the Mind Flayer from doing what they were up to.
This is a problem that only has a magical solution, and this was only a level 14 adventure.