The party feel very smug that they have managed to get passed the Mind Flayer, and all it took was a little sacrifice of some secondary character to appease the Mind Flayer.
For shame champions! For shame reader! Your champions are now -1 less heroic than they were before (negating the effect of any heroic weapons (tm)
Also, a little too smug."MWH-HH!" says the tentacle filled mouth of the Mind Flayer attached to the now much stronger Mind Flayer. He might have powered up, but he has by no means satiated his huge appetite.
'AH-HAH!' says the Mind of the Mind Flayer in mocking tones.
The party react quickly to the situation, shoving Stamm back out in front. Whether they know he is immune ot the effects or not, it just strikes me as the sort of unheroic thing your unheroic party would do.
Also, Stamm either still has the caterpillar, or in some form of sad acting out he has replaced the caterpillar with a dried twig twisted into his beard.
Go to 132 and face down the Mind Flayer, but note that the Mind Flayer is now twice as nasty as before, and Stamm may well have a penalty for feeling really sad now that he lost the real caterpillar!