|“||It [Truth-Teller] has never failed once. Some people say it is magic and will always strike true. It will serve you well.||”|
Truth-Teller is the name of Azriel's favorite magical knife that can help him discern the truth.
Truth-Teller is an obsidian-hilted hunting knife with a dark scabbard embossed with the name in silver Illyrian runes.
Truth-Teller is the twin to Gwydion, both forged from the iridium mined from the same meteorite. When the knife is near its twin Gwydion, it glows with dark light in response to Gwydion's white light.
Azriel uses his knife to torture the Attor after he tried to kidnap Feyre Archeron on the orders of the King of Hybern when she was practicing in the Forest near the Wall. He was caught before he could do so and taken by Azriel to the Court of Nightmares. After questioning him for information Rhysand told Azriel to break his legs and tear off his wings and then leave him on the coast of Hybern as a warning.
After Azriel was attacked by a naga in Hybern's war camp while helping Feyre free her sister, Elain Archeron, he was unable to participate in the final battle on the orders of a healer named Madja. Therefore he lends his knife to Elain, with whom he had developed a kind of bond so she would have protection, something that astonished Rhysand since he had never lent it to anyone. Elain used it to stab the neck of the King of Hybern when he was about to kill Nesta Archeron and Cassian and then Nesta ended up beheading the King with it.
- The following section contains details and spoilers for the Crescent City series
After Bryce Quinlan manages to escape the Asteri by opening a gate to travel through the worlds to reach Hel in order to request aid from the Princes, she accidentally lands somewhere in Velaris near the Sidra River instead, carrying with her the Starsword. Azriel finds her, blindfolds her, and flies her to a residence, carrying her to the living room.
A moment later, the doors to the foyer open and Amren, Cassian and Nesta appear. Bryce sees Amren first, then has the idea to try to communicate with them in the only other language she knew, the ancient language of the Fae, of the Starborn. Amren stagers back, surprised to hear her speak the language as no one has spoken it in their world for fifteen thousand years, and the others gape. Amren notices the Starsword and nods to Azriel's knife, Truth-Teller, at his side. The knife is the twin to the sword as it glimmers with dark light in answer to the sword's white light. Amren whispers that the Starsword is actually Gwydion.
- There is a Fae prophecy from Midgard that says: "When knife and sword are reunited, so shall our people be", referring to Gwydion and Truth-Teller.
- Iridium is one of the rarest elements in the earth's crust.