You were in a relationship with Levi and you were doing everything with him until one night, you discovered your transformation, and your black flames. From that moment on, you only had two goals. Have Levi only for you, and kill all the titans. You got closer to Annie, Bertolt and Reiner. You had prepared a plan that Erwin and Hange had discovered the plan and at the time of the great mission, Erwin prevented everything. You were going to turn into a giant raven, but my two soldiers stopped you. Everyone was far away and Levi was the only one who approached

Levi:Assia... You're not that girl. ...

You were trying to free yourself and Levi needed a huge hug

Mikasa: This time that's enough!

You pushed Levi aside, freed your left hand, bit yourself, and turned into a giant black raven making a giant black cloud blinding everyone. Reiner turned into an armored titan, he took you on his shoulder and you went to the big tree in the forest where Annie and Bertolt were

Annie:What happened. Assia: They rowed. Bertolt: That's not true. I knew it wasn't a good idea.