Head to the top of the Clock Tower and fire a charged bow shot at the Fire Bow symbol to expose the gears of the clock.

Once exposed, place down the Ragnarok DG-4 in front of the gears, powering a lever on the table on the bottom floor, to the left of the entrance door (right of the entrance if entering from the outside).

Step 2: Start the Clock

Once powered, flip the lever to start the clock, which will unfreeze the clock from 1:15 and begin ticking second by second. You must wait for the clock to reach the time 9:35, then flip the lever again to freeze the clock on that time.

When solo, the easiest way to do this is to watch the clock from the outside until it reaches 9:25, then as you make you way to the lever count the amount of ticks you hear until that number reaches tern and on the tenth tick, flip the lever to pause the clock. In co-op, you can just have your teammate call out when to flip the lever.

If done successfully, a bolt of lightning will strike the map, and a ball of lightning can be seen above the Pyramid in the Undercroft.

Step 3: Obtain the Plunger

Once the ball of lightning is above the Pyramid, wait for the Anti-Gravity to begin, and wall run against one of the glowing blue circular plates found around the Pyramid until you are teleported back in time.

This step can be a bit buggy and may take multiple wall run attempts to travel back in time, if it doesn't work within the first couple of tries, be patient and keep trying, the ball of lightning above the Pyramid means you are on the correct step.

Once teleported back in time, on the table opposite Dr. Groph's safe, will the Plunger you can interact with to obtain.

This Plunger has a hidden effect where, if you get the final hit on a Panzer, for one minute it will be transformed into a Flaming Plunger that instantly kills a Panzer, resetting the one-minute timer in the process. This can be extremely helpful during the main quest boss fight for chain-killing Panzers.

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