Tooth of Ammuk

The Tooth of Ammuk was a magical artifact that can absorb souls. Angel had one of them embedded into his body as part of his plans to resurrect Rupert Giles.

Effects
The Tooth of Ammuk absorbs fragments of a deceased person's soul whenever the user visits areas that were important to said deceased person in life. As seen with Angel, this results in the user taking on the soul's personality and mannerisms, though the user remains in control of himself/herself and is seemingly unaware of this.