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From Pathfinder Impossible Magic, which isn't enabled.

Nine Void Sleeves

ITEM 10
Price 1000 gp
Usage tattooed on the body
Bulk —

The ink on these tattoos, made from the crushed crystalline fangs and wingbones of sceaduinars, lends a dull purple-black hue to your arms and hands. During combat, the ink moves of its own accord, coalescing into nine smoky crystal spurs of darkness; these eerie finger-like protrusions move with an unearthly grace on your command, supplying the requisite magical gestures for your spells.

Activate—Shadow Fingers (concentrate, shadow, spellshape)
Frequency once per 10 minutes

Effect If your next action is to Cast a Spell with the void trait, your spell loses the manipulate trait and gains the shadow trait, as the tattoo's shadowy spurs perform the gestures in your stead.
Pathfinder Impossible MagicORC