
In Atomfall, players encounter a wealth of locked doors and fortified bunkers, making the discovery of various keys essential for exploration. Among these is the Castle Key, which can often leave players puzzled about its purpose or the location of its corresponding keyhole. If you’ve stumbled upon the hidden keyhole but haven’t yet located the key, this guide is here to assist you.
In the sections that follow, you’ll find a detailed explanation of where to locate the Castle Key in Atomfall, as well as instructions on how to use it.
Locating the Castle Key in Atomfall
The Castle Key can be discovered within the Castle Ruins situated at the Druid’s Camp in Casterfell Woods. To find it, start your journey by entering through the double grey doors at the front of the ruins.
Once inside, veer to the left and proceed through the kitchen area. Be vigilant as you scan the counters to your left; the Castle Key rests on one of these surfaces and is easily overlooked, often mistaken for crafting materials.

Using the Castle Key in Atomfall
After obtaining the Castle Key, make your way to the main banquet hall within the Castle Ruins. At the back of the hall, turn your attention to the fireplace. There, on its right side, you’ll find a hidden keyhole where you can insert the Castle Key.

When you use the key, the fireplace will shift, unveiling a passageway leading deeper into the Castle Ruins. If you haven’t yet explored this area through the side entrance from Druid’s Camp—a quick stroll from the main entrance—you’ll discover a network of caves filled with Druids and numerous loot opportunities, including an Atomic Battery.
Beyond the fireplace, to your right, lies a library. Here, you can acquire essential items such as the Strange Tonic Recipe, which aids in protecting against the Infection status effect, and Mother Jago’s Book, a necessary item for completing Mother Jago’s quest.
For further information about Atomfall, explore our guides on locating all Skill Manuals, investigating the murder in the church, and discovering the Site Office Key.
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