Step 3: Red Aethereal Orb
You will now need to assemble the recon rover located at the main bridge, and for that, you need to find a red aethereal orb.
The red aethereal orb is similar to the one you encounter during the random world side easter egg. You can find more information about the side easter egg here.
TOP GAMEPLAY HIGHLIGHTS
However, as the name suggests, the red aethereal orb is red in color and behaves slightly different from the regular aethereal orbs when shot at. It only flies in the direction you shoot it at.
You need to shoot the orb in the direction of the main bridge where the recon rover is. You can mark the bridge on the map overview to get a general sense of direction.
There are three orb locations in Sanatorium, and it can spawn in any one of them. The locations are as follows:
Red Aethereal Orb - Sanatorium Pool
In the middle of the Sanatorium Pool.
Red Aethereal Orb - Bathhouse Roof
On the roof of Bathhouse.
Red Aethereal Orb - Maintenance
On the roof of the Maintenance building.
Once you've found the orb, as mentioned before, shoot it in the direction of the main bridge. It will fly to a couple of places along the way to the bridge. You need to shoot it in the direction of the bridge every time it stops.
Once the orb reaches the bridge, it will stop on top of the modified recon rover. Ensure you do not shoot the orb once it is at its destination, as it can still move.
The orb will not go inside the modified recon rover. For that, you need a toy to lure it inside the cage of the rover. This takes us to our next step - The Aether Bunny step.
Step 4: Aether Bunny
The next step is to find a broken mystery box. As we already know, all the mystery box locations have a blue bunny as well. We need to find a broken mystery box, and it will also have a toy aether bunny on it.
The broken mystery box can be at any one of the mystery box locations on Sanatorium. Luckily, there are only three locations. Out of the three, we can always skip the active mystery box (the one that has a blue lightning beam coming out of it) as we're looking for a broken one.
The following are the three mystery box locations on Sanatorium.
Mystery Box Location 1 - Groundskeeping
Mystery Box Location 2 - Sanatorium Roof
Mystery Box Location 3 - Market Square
Once you've found the bunny, interact with it.
Upon interaction, the bunny will start to hover in mid-air, spawning a horde of zombies to attack you.
Eliminate all the spawned zombies.
Once you've killed all the zombies, the bunny will come back down and also drop a lot of valuable loot for you.
You can now pick up the bunny (now constantly glowing blue) and make your way to the modified recon rover at the main bridge. Once you pick it up, you will the same vision as the one seen when holding the canisters during the 'Retrieve' objective, and you also use the special ability.
You can also ride vehicles while holding the bunny.
Take it to the modified recon rover at the bridge and insert it into the rover cage to lure the orb into the recon rover.
The orb will fly into the rover, and it will drop another Omega Audio Recording. Interact with the radio to listen to a recording.
Once the recording finishes, you will get an option to activate the aetherium neutralizer.
Activatin the aetherium neutralizer will spawn in an energy field around you. This energy field or 'bubble' will move with the recon rover. You must stay inside the bubble as the rover moves forward.
Zombies are going to spawn and attack you as you move forward. The ammo is limited so make sure you stock up on ammo before activating the neutralizer.
Once you reach the Monument, the rover will crash into a wall and will be destroyed. The bubble will also disappear, but you won't get hurt outside the bubble anymore.
Make your way to the Monument. You can also get ammo on your way to the Monument.
Upon reaching the Monument, turn left towards the stairs leading up to the roof. Either take the stairs or use the rappel.
Go through the double doors and turn left to find the dead bodies of the scientists along with another Omega Audio Recording.
Play the audio recording, and once it finishes, it will play a loud alarm sound similar to the one that plays during the unknown radio signal easter eggs. It will attract all the zombies towards you, which takes us to our next and final step.