This sequence is also shown in a gameplay video.
A boss health bar for the Unknown Entity appears at the upper right corner of the screen, but you do not need to fight the creature directly. You can't destroy it yet. So just try and stay out of its way and avoid flaming spots on the floor, one of which is shown on Lara's right in the screenshot above.
These indicate where the monster's fireball attacks will land next.
The first goal is to activate each of the 4 circuit breakers by pressing Interact. The first one is just ahead and to the right of Lara's position when the initial cut scene finishes.
When each box has been turned on, the indicator light on top of it changes from red to green (as shown above) and a short cut scene shows one of four mechanical arms retracting from the central structure on the ceiling.
When you've used the first breaker, continue around the perimeter of the room to activate the others. Try rolling as you go to move faster and avoid the monster's attacks.
When all four breakers have been used, another cut scene shows four large electrodes descending from the ceiling. The sword fragment is held in some kind of force field at the center.
Now run to the Tesla gun in the middle of the room and press Interact to get on.
The step shown in this screenshot and the next one may not be necessary if you deal with the electrodes quickly, but you can also use the Tesla gun to get the monster out of the way temporarily. First use 'pull' (G/L1/LT) to immobilize the creature.
Then drag it into position between two of the live electrodes against the wall. Then 'push' (left mouse/R1/RT) the creature into the arcing electric current. When you do this, the monster will disappear for a few moments, and you'll see its health bar diminish temporarily (as shown here).
The critical part is to target each of the large, dangling electrodes.
Tap the fire button to push each electrode away until it makes a connection with the pair of live electrodes against the wall. (Two good pushes should do it.)
Repeat the process with the other three electrodes, swinging the gun around to target each one in turn. You must do this quickly for all four to be activated at the same time. When this happens, the circuit is completed, and electricity arcs between the electrode you are pushing and the neighboring electrodes.
Activating the Tesla experiment this way also removes the force field around the sword fragment. Get off the gun, point the camera at the sword fragment hanging directly above the gun. . .
. . . and quickly press Grapple to snag it.
As soon as Lara grapples the sword fragment, a cut scene begins.
The main walkthrough includes a few additional tips, in case you need them.
[Return to the Kazakhstan Walkthrough]