Einzbern Forest is a large forest on the edge of Shinto. It is the location of most of Berserker's battles as well as the battle between Kirei and Hasan. It is where Shiro first used Archer's arm to use Nine Lives, which he used to instantly kill Berserker.
The layout of the stage is simple. It's an all direction loop with numerous trees placed everywhere. It is a fair battlefield for everyone.