Feed the Growth Stimulant to Oberon
When you have the Growth Stimulant, you have everything you need to enter the Oberon facility in the Interchange. To do that, you need to power up every single Data Store Room in the Interchange and then turn on the Central Processing Unit located in the central room. Once the CPU is powered on, a new entrance to the Windscale Plant will become available.
Take the Windscale Plant entrance to access the new area with Oberon. You have to go through the Windscale Plant before reaching Oberon, which is full of thrall enemies. But after you get through the plant, you’ll be in the Oberon Digsite area. Here, you need to take the Growth Stimulant and head to the large building located to the immediate left of the digsite entrance. This is found before you reach the purple-glowing Oberon rock.
Inside this building, you have to navigate through a series of hallways, sometimes defeating enemies in haz-mat suits, until you reach the command center of the digsite. On one of the command center consoles, you’ll find the “Fire Safety Fluid Input Terminal.” You need to insert the Growth Stimulant into this terminal.
Once that happens, head down to Oberon itself, being careful to avoid the patrolling robots on the ground level, and find two “Fire Safety Valves.” These are located on either end of the digsite and require a simple interaction to use. Now, you can head back up to the command center in the building and turn on the “Fire Safety Valves.”
After these are activated, head back down to the digsite once more. Exit the Oberon Digsite area, make your way back through the Windscale Plant, and go to the Castle Ruins at the Druid’s Camp in Casterfell Woods. There, jump into the blue glowing hole in the ground at the command of the Voice in the Soil. This ends Atomfall.