Description

A bell.
A candle.
A book.
The witch's notes on the current threat. 'First you will need a bell. Any sort will do, even a really small one. Next you'll need a book, but not just any one. You'll probably need one of the books the cult uses, which will be in the mansion. Then you'll need a candle, the sort that might be used in dark rituals. I suspect one is in the dungeon. Then, take all three items to the dark altar past the mansion and read this incantation (the parchment then trails off into some language you don't know and hope you'll be able to pronounce).

Type

The reception desk bell can be found when you defeat the Robobellboy in the Hotel. You can also use the Cat Bell (found for sale in the dungeon shop once the Doom Quest starts or by obtaining the Catgirl class), the Cow Bell (from one of the Cowgirl classes), or the Kraken bell, a slap weapon that can be found by diving in the lake in the Dungeon region.
The black candle can be obtained by defeating or trading with the gladiator in the Dungeon or the Dominatrix in the Hotel. There is also a cock candle found in the room with the Alchemist's bowl in the dungeon.
The Pocket Necronomicon from the pedestal display case in the Mansion's Private Library. Additional books that work for the ritual include Brandi's Big Book of Anal and the Book of Do-overs. These books can appear on a pedestal in the Private Library in the Mansion, the Junk Room in the Academy or will occasionally appear for sale in the Dungeon Shop (starting with release 13 version 7.0). If you have used one of these books to craft the hands-free notebook at an Alchemist's bowl, either in the Dungeon or in the Academy, this will work as well. Additionally, the romance novel which is found in containers currently counts as book for the ritual.
The notes are given to the player by the Witch in the Witch's Shack in the forest region once the Doom Quest has been triggered.