The necklace was procured by Abby and her husband as a gift from gypsies. For many years they allowed this group to camp on their lands near the property line for free with no payments, all they asked in return was kindness and to treat the land with respect. Suspected but never confirmed this particular group had a direct lineage line to the ones that cursed Angel. It is unknown however that the gypsies knew Darla was now a vampire, and gave the necklace to Abby to protect her.

 The necklace was said to be able to bring the good parts of ones self to the surface no matter how dark the soul. Darla's childhood friend wore it all her life and helped to power it up with goodness that came from her happy and thankful soul. Abby's mother had died in childbirth and she never knew her father who died at sea. The orphanage gave her the last name Smythe however she took the last name Addams when she took Darla's place in adoption and later her adopted families name Crichton. Her family is thought to be ancestors of Michael Crichton, who wrote Jurassic Park among many other popular and successful novels. Her husband's name was James Summers and though Darla doesn't know, the Doctor confirmed James and Abby are direct ancestors to Buffy and Dawn. In fact Dawn bears a striking resemblance to Abby which Darla has most definitely noticed but never spoke of given her childhood pain and loss. 

The necklace itself slowly bonded with Darla's spirit and over the decades brought her light side back and given its center is the silhouette of a cat. Though the jewel itself is said to have been forged at the same time Excalibur was and has a link to the Arthurian legends. She has for a better expression nine lives to live which would present her with longer than normal life span. When removed from Darla for any period of time she retains all good this object has given her but without her it now becomes a dark cursed symbiotic object. The object draws on light and good energy and transverses it to Darla's being from happy childhood memories to inspirational positive thoughts. That is why this particular Darla usually has her upper body uncovered as much as possible she feels so happy and alive doing so. The Doctor also knows but has never told Darla that the Gem of Amara is unnecessary given she is almost super human abilities and performance thanks to her belly ring. For lack of a better term she is like an vampire Wonder Woman minus a magic lasso of course. 

Wolfram and Hart wish to use its now dark nature to bring the dark side of humanity to the surface along with the dark side of all the known benevolent magical objects in existence and symbiotic link them to the ring. Therefore a new dark age of man would transpire and no man or no vampire could stop it. Except King Arthur and that would require a trip to Avalon in the present or a trip to Camelot of the past something the Doctor wishes to avoid. To obtain this the Doctor had chosen different eras in history where Darla was indisposed, distracted, or unconscious whether to pleasure, pain or more to grab this item. In parts of the story these early attempts might likely fail which might entice Buffy and company to seek out additional professional help in this area.