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The Knife was the disguised Book of Dweia. The Knife was primarily used by Eliar throughout the story. Its main purposes were to reveal each of Althalus' team member's purpose and to travel through time and space using the House at the End of the World. Any agent of Daeva who looked upon the knife would cringe and scream, potentially going insane through long exposure.

The Knife was sought and found by Althalus. Eliar had taken the knife from Chief Albron's armoury before going to war in Treborea. Althalus allowed Eliar to keep the knife, as Eliar was the only one capable of using it to travel through time and space.

At the end of the story, the Knife changes back into the Book of Dweia, where it burned the Book of Daeva together with the Book of Deiwos. Presumably, the Knife/Book remained in the House with Althalus and Dweia, as it is mentioned that all of the doors were closed off, removing the purpose of the Knife.