Play the third battle, where you control Cassie, the spider, and a despaired man. Cassie is the only one that must reach the safe zone to end the battle. Use your spider to break barrels to access the chest, then hide the spider behind it. Go for the lever with the man as quickly as possible to open the gate. Pass through the gate with Cassie, and reach the door. Hit the lever, then run to the safe zone to get the "No Blood! No Blood!" achievement.