In the previous post I mentioned the M. R. James ghost story "The Treasure of Abbot Thomas." The protagonist, Somerton, follows a trail of cryptic clues to a treasure of ten thousand gold pieces from an old manuscript and stained glass window, ending up in a ruined abbey. Everything that happens next - the assembling of equipment, checking for traps, hidden compartment finding - is straight out of the adventurer's manual. What he finds there, though, is straight out of the adversarial dungeon master's menagerie...
This creature rounds out the other two M. R. James-inspired monsters in my Varlets & Vermin compilation. I can't help but think that even a level 1 adventurer would have been made of sterner stuff than Somerton; would have put the toad to the sword, or at least come back in the daytime better-prepared. But maybe the toad was made of sterner stuff, too?
Armor Class: 7 
Hit Dice: 2
Attacks: 4 tentacles, 1d2 each
Saving Throw: 16
Special: Tracking, surprise, attachment
Challenge Level/XP: 2/30
Treasures owned or hidden away by priests and wizards of doubtful morality are infrequently guarded by the loathesome sack custodian; although the ritual used to summon it is not part of common knowledge. The rounded back of this toad-like creature blends chameleon-like with the other sacks that form the treasure. It will manage to be the topmost and foremost in the trove, and gains automatic surprise if picked up. The custodian's underside conceals a squashed, squinting face, four stumpy legs, and a mass of sharp, slimy tentacles exuding a strong smell of mold.
Its first attack, ignoring armor, is merely to latch on to the victim. Each round after it succeeds in this, four of the tentacles attack, ignoring any dexterity bonuses. It requires a strength test similar to opening a stuck door to pull the custodian off. If fled from, the custodian is an unerring tracker, moving only by night. It will persecute the disturbers of its trove until everything is put back the way it was. Rumor has it that not even killing the custodian will stop its pursuit, but what - if anything - can finally put it to rest, other than the return of its treasure, is unknown.