So just to put it in perspective:

Charmcaster was part of a family of 13 siblings, she was the second youngest of her family, the poucher killed her parents first before kidnapping her and her siblings. 
To tell them apart when they were younger since they looked alike,the parents gave each sibling a large stick that had a Zodiac symbol caved into it which would remain on the stick and as with all wood when the stick would start to wilted away. They would have a necklace created with their symbol.

Charmcaster was forced to watch as each of her sibling were experimented on and as each of them died a slow painful death apart from two, Charmcaster and her youngest sister, however while Charmcaster survived the experiments with her mind intact somewhat, her sibling did not and her mind was broken beyond repair.

Charmcaster heard of the terrible things the poucher would do to her broken sibling and did not want her to suffer like that, so to spare her, Charmcaster did what had to be done and caused a massive explosion destroying the base she was trapped in. Taking the lives of the pouchers and saving her sister from a terrible fate, though she stayed with her sister in.her final moments.

Once she was free and had buried her sister, Charmcaster carved all her Sibling symbols into her own wand to never forget them and as a way to promise them,vthat she would seek vengeance upon those that hurt them. She would later meet Serina, Zelina and Gilata who had all suffer because of the pouchers and join Selina on her crusade.