Anima Colligationem

 was a magical artifact capable of tying one's soul to the stone itself. In 2019, the Siphon created the soul tie stone from Willow Rosenberg's own soul, so half of hers would be placed in the recently sired Alexander Harris.

Behind the scenes

 * "Anima colligationem" is Latin for "soul tie".

Appearances

 * Frenemies
 * Buffy the Vampire Slayer #5
 * Buffy the Vampire Slayer #6
 * Buffy the Vampire Slayer #7