The Big Sister 1/3 boss fight is one of The Surge’s cooler set pieces. After climbing the central cooling tower in the second area, fall down onto the moving machine. The boss will come to life and Phase 1 will begin.
Phase 1: The claws
The arms of the Big Sister 1⁄3 will come after you in this first section. Only one will attack at a time. Use your lock on and target swapping button to stay focused on the arm that is currently winding up. The boss will also occasionally shoot a laser at you from the back, so watch out for that.
The claws will do a variety of attacks, most of which involve stabbing at you or trying to smash you into little pieces. Keep an eye on them and dodge out of the way before they hit. After they strike, the arms will pause in place for a brief moment. Damage them in this brief window.
Repeat this process of dodge, strike, dodge, strike until the claws are destroyed. The platforms will come together and you can proceed.
Phase 2: The torches
By moving forward, you will find yourself in a new hellscape filled with fiery robot arms. The torches themselves are weak, but there are four of them trying to attack you at once. Pick a side and go to town.
This phase is very fast and hectic. Take out the torches whenever you can and watch out for the boss’ thrust attacks. Use the dodge-strike maneuver to stay limber. Once all the torches have been destroyed, the boss’ core will emerge.
Phase 3: The core
Attack the center console to lure the eye down. Big Sister 1/3’s core is surrounded by creepy spider arms. These arms can grab you, smash you, punch you or maim you. Try and stay limber when you are around them. Dodge more frequently than you attack, and be ready to move at any moment.
Attack the core with all that you have and then jump back. Wait for the boss to calm down for a moment and go back in. Watch for the arms to open up and jerk toward you. Dodge this, as the grab is very powerful. Once you have whaled on the core for a little bit, Big Sister 1/3 will be destroyed.