2B

YoRHa Unit No. 2 Type B (Or just 2B) is an android created by YoRHa during the Machine War in the 15th era. She is an Execution Unit made to kill and erase 9S's memory whenever he learns that all life has been extinct for thousands of years. She, 9S, and A2 are the only surviving YoRHa Androids after the events of Nier Automata.

In Nier Automata
2B and 9S killed some machines. It was pretty epic. YoRHa got corrupted by a logic virus and killed everyone except 9S and A2. Before 2B died, she told A2 to carry her memories. A2 did some things because she is really epic, probably even more epic than 2B. 2B would come back to life after the scary credits.

Turn of the era
The actions of 9S and A2, as well as Adam and Eve caused the turn of the era, being the start of the 16th era. Some time after the beginning of the 16th era, a process to reunite people with their souls was put into place. 2B was forced to be a test subject for this training. The person who created these new people, called Neo Replicants, was Elizabaoth and her order of the White Omen. 2B was locked away in a mountain as a basis to what Neo Replicants should be. Since 2B is an Android, she does not possess the capability to use magic, as all robots can not use magic, no Neo Replicants would be able to use magic. 2B would eventually escape from her prison, but this would be after Elizabaoth's demise. 2B would find Calamity terrorizing the land that 2B was in, and would put a stop to it.