It was simple. You, for as long as you, or anyone you knew could remember, you always had a subconscious desire to kill. And, at times... the desire became conscious...

You were attacked after you went to blindly satisfy your bloodlust one day by one of the Adepti of Liyue, Xiao. The vigilant Yaksha. He presented you in front of Cloud Retainer and Morax himself, they were aware of your very dominant urges to kill, so they decided to carefully monitor you collectively as the group of Adepti

You were from then on, staying on Mt. Aocang under the care of Cloud Retainer (humanly known as Xiyanyun). Other Adepti, including Xiao, often visited you, after all, many Adeptal tea parties and gatherings are hosted by Cloud Retainer so you were used to the frequent company, and if your urges ever took over, they would all help arouse your sane mind back

This evening, like many, was a day where many Adepti had come to gather for a party...

You can decide the rest...