Type-O Demon Fun
I've used the book a good bit the past two sessions. First, a party member was killed by a trapper that had made a home in the local inn. After they raised him, the party went to an inn in the next town (which proudly posted a sign that declared itself "Trapper free for the the past 7 days").
During the night, a gang of slaadi with unusually low intelligence came to the inn, looking to steal food stuffs (cheese and some dried bread the innkeeper had planned to use for croutons). Each slaad carried an interesting weapon, one a large trident with thick tines, another a large mancatcher/pincer device, and the third a wooden mace that emitted a black powder when the head of the mace was turned. After besting several of the slaadi, the party was able to strike up some conversation with them. The slaadi reported that they were seeking to make their lord comfortable and wanted the party ranger to cast speak with plants for them, so they could communicate with their master. It seems that while the slaadi were traveling to this plane, they were separated from their master. They were now seeking out their master in this plane, believing that the master had assumed his true form.
The party agreed to speak with the master of the slaadi. A brass dragon (mock dragon, actually, from CC I) came forward, carrying a large wooden reversed dome on its back. Inside the dome, was a mass of rotting, black vegetation. The party tried to speak with the dragon, but the slaadi corrected them, saying that their lord was inside the bowl on the dragon's back. The party noted their confusion, so the slaadi gave them a copy of an ancient book, the Tome of Horrors, and pointed out how they had discovered their master's true form. There, on page 234 of the book, was the answer. The Slaad Lord of Entropy's true form, a 15-foot tall black salad. Then, the slaadi came forward with their large fork, salad tongs, and pepper grinder and made their master "comfortable".
Sure it took a good four hours to set up the joke, but it was well worth it. The look on the party's faces was priceless. They assured me that this was an adventure that they would remember for a long time.
The Tome of Horrors is a great book, typos and all.