Reinforcement in Overwatch
A diary of a mysterious Chinese alpinist Mei-Ling Zhou was published on the game's official website. It seems Mei-Ling will become the next hero to be introduced in Overwatch. According to the journal, she specializes in abnormal climate phenomena. Mei used to work with another Overwatch hero - Winston. She pays much attention to the description of equipment, which enables to work at low temperatures. One of the instruments, endothermic diffuser, enabled Mai Ling Zhou to built a walkway through mountains and make a shortcut.
The last hero is possibly Mai-Ling Zhou
No additional information has been provided yet apart from the journal and the image with silhouettes. Most likely her main weapon or ability will influence the temperature of the aim or environment. However, we can't tell for sure.