There is a Legacy version
here.

Shadewither Key
Item 22This Item may contain spoilers from the Gatewalkers Adventure Path
Unique Artifact Cursed Illusion Invested Primal Shadow Source Gatewalkers (Hardcover) pg. 229Usage worn;
Bulk —
This palm-sized talisman hangs on a string of braided bark fibers. It resembles a leaf from some unknown tree similar to oak, carved from jade and then dipped halfway into black ink that looks wet despite feeling completely dry. The gate key was originally created to open the aiudara known as the Seventh Arch. In recent years, corrupting magic has given it additional, stranger powers.
When you wear and invest the
Shadewither Key, shadows gather around you. You gain a +1 item bonus to
Stealth checks. However, this boon comes with great risk: any
elf who touches the
Shadewither Key is immediately afflicted with the
obnubilate curse.
Activate—Umbral Double [three-actions] (
concentrate,
manipulate);
Effect You touch the
Shadewither Key and command the shadows it casts around you to peel away. The shadows form an umbral double that resembles you in every way except for its fiery red eyes and the expression of wicked delight on its face. The double occupies the same space as you and attempts to intercept any attacks aimed at you. A creature must succeed at a DC 11
flat check when targeting you with an attack, spell, or other effect; on a failure, they hit the shadowy double instead of you. The effect lasts for 1 minute or until the double is hit, whichever comes first. Once the double is hit, it’s destroyed. As long as the double exists, you don’t gain the
Shadewither Key’s item bonus to Stealth checks.
Destruction The
Shadewither Key’s magic can be destroyed by exposing the artifact to uncontained teleportation energies. If touched to an unlinked or malfunctioning aiudara, the
Shadewither Key causes the gate to connect to a new counterpart. If this happens, the key’s magic leaves it, rendering the item useless (as described in the book).