He pressed something cold into her hand. A knife. It was all white and all of a piece, hilt and blade, as if hewn from a single bone. Its pommel was carved with the faces of three women, or perhaps of one woman at three different ages: maiden, lady, hag. It didn't warm to Jame's touch.
– Jame's narration, Dark of the Moon, "Chapter 13: Converging Paths"
The Knife is associated specifically Regonereth, the aspect of destruction. Since Jame is Nemesis, the avatar of Regonereth and one of the Tyr-ridan, the Knife has an affinity for her.
The Knife itself is described in Seeker's Mask by Kirien as being approximately twelve inches long and double-edged, and appearing carved out of one piece of ivory for blade, guard and pommel (the material for the grip is not specified). The Knife is noticeably cold to the touch. The Ivory Knife's blade kills everything and anything it cuts, no matter how minutely; it is described traditionally as "the very tooth of death". When the Knife falls to the ground, the grass and plants around it begin to die. It rots inanimate objects it touches, like fabric and floors.
On the pommel are carved the three faces of Regonereth (Maiden, Lady and Hag). The face of the Maiden seems to be Jame's own, just as the faces of the Lady and the Hag, respectively, appear to be those of Jamethiel Dream-weaver and Brenwyr. All are Shanir aligned with the Third Face of God, and potential incarnations of Regonereth.
Jame is capable of seeing out of the eyes of the Maiden face on the pommel, but has no control over it.
↑God Stalk, Book II: Crown of Nights, "Chapter 7: The Feast of Fools" — " 'Flee, man, flee, and we will follow.' And so he fled, Cloak, Knife and Book abandoning, into the new world."
↑Seeker's Mask, "Part I", VI — "The Book, the Ivory Knife, and the Serpent-skin Cloak—those three object of great if ambiguous power kept by the Master in Perimal Darkling after the Fall. No one knew what roles they might play in the final conflict, only that each was necessary."
↑Seeker's Mask, "Part V: Mount Alban", V — " 'Item: one weapon, classified knife or dagger; approximately twelve inches long; double edged; composition: ivory […] carved all of one piece, blade, guard, and pommel; and on that last shall you see the three faces of Regonereth—maiden, lady, hag—and know what you hold by its coldness. The very tooth of death…' "
↑Seeker's Mask, "Part II: Gothregor", V — "Under it, the grass began to die."
↑Dark of the Moon, "Chapter 16: Blood Rites" — "The tough fabric ripped, half cut, half rotted by the Knife's cold edge."
↑Seeker's Mask, "Part II: Gothregor", V — "The blade dropped with a deadly thunk, to quiver upright in the floor which began to rot at its cold touch."
↑Seeker's Mask, "Part VI: Mount Alban", V — "It wasn't her knife at all, although for a moment she thought that her own face stared back at her, naked and hag-like, from the carved ivory pommel."
↑Dark of the Moon, "Chapter 16: Blood Rites" — "Jame glanced from it to the pommel of the Knife and back again in amazement. Yes, of the three faces carved there—maiden, lady, hag—the Mistress's was the second."
↑Seeker's Mask, "Part II: Gothregor", V — "Of the three aspects carved on its pommel—hag, lady, and maiden—the third smiled back at her with a face so nearly her own."