Jade Hairpin

Jade Hairpin is a hairpin consists of two intertwined jade snakes. It was created by Owner of Precious Jade, and originally belonged to Snake Mother. Later, Snake Mother gave it to Blanca and commanded her to assassinate the General. However, Blanca found that she couldn't use it, so she visited Precious Jade Workshop and asked Fox Fairy to modify it. Although Fox Fairy fulfilled Blanca's request, the modification wasn't prefect. If Blanca uses it to channel her magic, it will also drain a part of her memory.

Abilities
Jade Hairpin is designed to drain other's magic and transfer it to its owner. To do that, Jade Hairpin need to physically contact its victim first. In the movie, Snake Mother used it to drain General's magic from a distance, however Blanca still needed to have physical contact with Jade Hairpin to activate it.

Besides draining other's magic, Blanca also used it to channel her magic for difficult tasks. However, since she wasn't its original owner, as a side effect, every time she used it, Jade Hairpin would drain a part of her memory.

Moreover, Jade Hairpin seems to be semi-sentient or able to protect its owner. In Blanca's memory, when she was falling from the waterfall, Jade Hairpin protect her from the injuries of falling.

As noted by the Owner of Precious Jade, Blanca's modification of the hairpin allows her to use its powers, but has the side effect of consuming her memory. This side effect occurred several times in the story. The first instance appear at the intro when she fell into the water, the hairpin saved her, at the cost of memory loss. The second instance appears when she drain the energy of the little general, which made her powerful, at the cost of memory loss again. The third instance appears near the end scene, where she protected Sean's soul from disintegration, at the cost of her powers and memories.

The Snake Mother, being the original owner of the hairpin, is able to use its powers without consequences. Additionally, both the Snake Mother and the General are able to drain powers from the other snakes without the use of the hairpin.

Trivia

 * In traditional Chinese culture, hairpin is considered as a token of Love. In ancient romance stories, hairpins, especially those made of precious materials, served the same purpose as modern day's engagement rings. Hence, in the past,  helping a girl to put on her hairpin was a very intimate behavior which only happened between married couples or family members.