Restore Power to the Ward
To restore power to the ward, you'll need to locate fuses and solve a color-coded puzzle. Your journey begins in a cave tunnel, where you should head towards the light. Don't turn left at the first intersection. In the orange-lit area, find a radio, an item box, and a map on the wall between them.
Your first objective is to retrieve the Small Circular Piece. Use the map to navigate to the southwest portion of the maze. Go down one corridor from the save point, then turn right. You'll pass a stone mural on the right before reaching a triangular podium. Grab the piece from the podium, then return to the save point area. If you go north (left) at the second intersection on your way back, you'll find a glowing red sign from the subway area, an area of interest not on the map.
In the arena, as Roman, run towards the back wall to the left from your starting position. Stand near the collapsed pillar on the floor. Allow the Abomination to smash down on it, freeing a revolving mechanism (a rotating floor) for a later puzzle.
When controlling Freya, ignore the console directly in front of her on the high walkway. Run to her left (her right) to the first console with a border. This allows her to pass a gate Roman is holding open. Switch back to Roman.
As Roman, release the lever. Turn around and go to the right (back where you came from). Locate two circular pressure pads. The one closest to the boss spawns a bloody enemy (Baby Face). The other, closer to the back wall, raises a gate covering another lever.
To activate the gate, use the pressure pad closest to the boss to spawn an enemy. Lure this enemy to the back pressure pad (closest to the outer wall) and kill it there. The enemy's weight will keep the pad active. To prevent the boss from smashing the enemy, run left after spawning the enemy to draw the boss's attention, then move back to lure the enemy to the pad.
To find a fuse, turn your attention to the unlocked door on the right, leading to a control room with a fuse box. Facing this door, step behind the vending machines to its left. A yellow door with an eye symbol is behind them. A vending machine to the left of this door has a mannequin hand sticking out; take the Fuse (1/3) from it. Then, open the yellow door to enter a corridor with organic tissue, and open the next door.
You will encounter a combination lock panel requiring "413". Once powered, it flashes "Red, Blue, Red, Green, Blue". This color pattern is a clue for a corridor with lights above doors. Go back outside the room to investigate.