Cassandra Wu-San is the daughter of League of Shadows-member Lady Shiva. From an early age, she was subjected to a brutal regime by her mother to make her the perfect assassin. This included damaging her vocal cords, so the only language she would learn was body language. This also left her body, and particularly her face, covered in scars.
Her first mission was to be one for the Light: Joker was dissatisfied when he learned the true purpose of the Injustice League, and threatened to blow up the United Nations. Cassandra would have to take him out. She observed from the shadows as Batman and his protegés defused his bombs, and as he escaped in the dark, she saw her chance to strike. Before she could land the swing of her sword, Batgirl pushed him away and took the hit. It hit her spine and immobilized her from the waist down, and she explained to Cassandra that she did not do it to save Joker's life, but rather hers. Batman trained her with his team, with Cassandra adopting "Orphan" as her codename. He also vouched for her to the Team, so she could be trusted despite her inability to speak, or learn her true identity through a full face mask.
Robin and his squad were doing a routine check on Mad Hatter, who was recently released from Arkham Asylum. After Robin discovered the crook left clay behind, Orphan rushed ahead and cut Mad Hatter in two with her sword—revealing him to be Clayface. They followed him to a warehouse, where the real Mad Hatter oversaw Blackwater meta-human smuggling ring. The squad fought the mind-controlled Clayface, but Mad Hatter blew up the warehouse as he escaped. Orphan and the others made it out safely.
Swordsmanship: As a former member of the League of Shadows, Orphan was raised by Lady Shiva to be the ultimate assassin and weapon. She is trained in swordsmanship, as she skillfully cut Clayface in two with her sword, and later sliced him apart once more. She also cut through Black Spider's webbing with ease.
Marksmanship: Orphan can also throw Batarangs and use a bow and arrow.
Acrobatics: Orphan is very agile, as seen when she evaded Clayface and comfortably dropped into a room from the ceiling.