Once they got to the scene, the mind flayer revealed its identity, announced that it was there to kill them as vengeance for slaying the son of Evard the Black (who is essentially my game's Voldemort), and the "standing stone" opened its baleful eye and maw and revealed itself to be a roper.
The fight didn't open well ... the mind flayer's mental blast stunned laurie_robey and the NPC monk/cleric right off the bat, camstone's ranger was hit with a massive strength drain from the roper's strands. Fortunately, jamesbarrett's fighter came bounding in to engage the roper, giving camstone the opportunity to get away. jamesbarrett's wizard started blasting the mind flayer (I forget its spell resistance until near the end, but since I'd given it a few other boosts, particularly magic armor and of course the alter self potion, I figure it about evens out), giving camstone the chance to bring it down with his arcane archery. (Fortunately, STR drain doesn't hurt your bowmanship!) Unfortunately, the mind flayer had managed to charm pholph's bard, causing him to take potshots at the wizard instead of helping with the fight.
Once the mind flayer was down and the group could concentrate on the roper, the rest of the fight went fairly quickly. The fighter got kinda chewed up, but well within survivability; by making the roper concentrate on him, he kept the ranger from being a roper snack. I seem to recall it was the ranger who got the killing shot on the roper as well, but it was definitely a group effort. All in all, nice teamwork all around. (Except, alas, for Laurie, who got unstunned just as the roper fell.)
Next week, pholph is not available and camstone asked for a break. I might try to run my long-neglected Star Wars game, and just say that pholph's Jedi Guardian is off on another mission somewhere.