The Protection Amulet is a magical necklace imbued with concentrated protection from good witchcraft. The warlock Anton somehow came into possession of it some time during or prior the 1920s, and gave it to P. Russell, his love. Their plan was to kill and obtain Russell's cousins' powers: P. Bowen's cryokinesis and P. Baxter's molecular deceleration, and it was only while armed with the amulet were they able to stand a chance against them. However, Phoebe Halliwell, a future-incarnation of Russell's, possessed her past-self's body and, being a good witch, knocked out Anton, giving Bowen and Johnson the time to pin her down and rip the amulet from her neck, before casting a curse that killed her. Unfortunately, Anton retrieved the amulet and escaped, waiting for Russell's future-incarnation to visit Christina Larson, who witnessed Russell's death.
When Anton heard that Phoebe had visited Larson, he glamoured into the old lady and pretended to be her when Phoebe and Leo visited. After Phoebe cast a spell to switch life forces with Russell in the past, Anton took the amulet out of a drawer, knocked out Leo, and put the necklace around Phoebe's neck. However, the spell wasn't a possession spell, as such, but a soul-switching spell, so Russell awoke in Phoebe's body with Anton, who told her that they had to steal her future-self's sisters, Prue and Piper Halliwell. They arrived at the Halliwell Manor, where Prue and Piper realised they could not use their magic on them because of the amulet, and that Phoebe, in the past, could not get back into her own body because of the necklace's power. Fortunately, Prue managed to deflect a stream of fire that Russell sent flying at her and vanquished Anton, leaving Russell devastated and easily subdued. With the amulet removed, Phoebe returned to her body and the amulet protected her from the curse Bowen and Baxter had put on her past-life. What happened to the amulet afterwards is unknown.
The creation of the Protection Amulet is unknown, though it was presumably created by evil to be used against good, much like the Eye of Aghbar owned by the Demonic Forty Thieves and later used by Bosk. Because of its power, it is likely a wizard, demonic sorcerer or some other powerful dark being created and bespelled it. At an unknown time during or before the 1920s, the warlock Anton got hold of it.
P. Russell was given this amulet by her lover, the warlock Anton. It was to protect her from her cousins, P. Bowen and P. Baxter. Whenever they attacked her, the amulet would suck up whatever was attacking her like when Phoebe attacked her with her ice breath.
Phoebe Bowen and P. Baxter tore the amulet off of Pearl's neck after catching her and holding her down. A little girl named Christina Larson saw it lying on the floor. Right after they had torn it off, Phoebe and P. Baxter used a curse to kill their evil cousin and all of her future lives.
In 2000, Phoebe Halliwell got warned by her past life Pearl Russell that her life was in danger. Phoebe therefore cast a spell that would take her to her past life. To know more she visited the only person alive that could remember what happened, Christina Larson. She told Phoebe and her sisters about a "pretty necklace" that got torn off the bad witch's neck and slid across the floor.
Phoebe cast the spell again and went looking for the necklace but could not find it. This was because the warlock Anton had already taken it. To give herself more time to look for it, Phoebe switched lives with Pearl but in the present, Anton knew this and glamoured into Christina to trick Phoebe.
He gave the necklace to Pearl, who was now in Phoebe's body, and went to the Halliwell Manor to kill Prue and Piper. Their plan failed and the sisters vanquished Anton. They took the necklace off, allowing Phoebe to switch lives back and put it immediately on once Phoebe had returned. The amulet glowed as it absorbed the curse and Phoebe was safe, but it is unknown what the sisters did with the amulet afterwards.
The Protection Amulet appeared in a total of 2 episodes throughout the course of the series.