Mycopunk Cranius is one of those secret bosses you could walk right past without realizing there’s an entire fight beneath your feet. He’s hiding under a giant mushroom in Moldy Tundra, near an old silo. Because apparently, a giant mushroom wasn’t suspicious enough on its own.
The tricky part is actually finding the right spot. Mycopunk’s 2026 update introduced procedurally generated maps, so you could spend ages looking for a landmark that isn’t there. Here’s how to reach Cranius without turning the whole thing into a mushroom-hunting expedition.
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Where to Find Cranius in Mycopunk
Before starting a mission in Moldy Tundra, check your map selection. Look for the Permanent Location option in the upper-left corner of the mission-selection screen. This lets you access the original handcrafted maps, which are still available alongside the newer randomly generated levels.
On the original Moldy Tundra map, look for a large circular building resembling a silo near one of the map’s corners. To the right of it, you’ll find an enormous red mushroom with a cage-like structure.
Head underneath the mushroom and look for a hole in the ground. Drop through it to reach a hidden area with a console. Activate the console to open the way into a secret sublevel. When you get inside, head toward the large structure in the distance. Climb to the top and drop into the arena below to trigger the Cranius boss fight.
How to Beat Cranius in Mycopunk
Cranius can spew explosives, so standing still and trading damage isn’t the best idea. Keep moving during the fight and give yourself enough room to dodge incoming attacks.
I’d also clear out any enemies following you before climbing the tower. You don’t need extra trouble when you’re already heading into a hidden boss arena.
A loadout focused on reliable damage is a sensible choice here. If your weapons aren’t keeping up, our Mycopunk build guide explains how to make better use of the game’s upgrade grid. When Cranius is defeated, you can call in the drop pod to return to the HUB.
Cranius Rewards and Weekly Reset
Cranius offers weekly upgrade rewards, making him worth revisiting after your first victory.
The September 2025 reward update added one extra Saxonite and two additional upgrades to his weekly rewards, with one of those upgrades guaranteed to be Exotic. The same update increased the rewards for additional kills after your first weekly clear.
A later patch also fixed duplicate protection for Cranius’s weekly Exotic upgrade. That makes the first weekly kill especially valuable if you’re looking to expand your upgrade collection.
How to Unlock the Cranius Achievement
To unlock the Cranius achievement in Mycopunk, you simply need to defeat the secret boss. The achievement was bugged when version 1.0 launched on October 20, 2026, but patch 2.0.1 fixed the issue on October 21.
If you come across older information claiming the achievement is broken, that particular launch bug has already been addressed. If you’re hunting other boss-related unlocks, Expedition Alpha is another encounter worth checking out, since completing it unlocks the Mycologist.
Can’t Find Cranius in Mycopunk? Check Your Map
If the giant mushroom or nearby silo seems to be missing, double-check your selected map. The April 2026 World Update introduced randomly generated levels while keeping the original maps available. The entrance described above uses landmarks from the original Moldy Tundra layout.
Select Permanent Location before following the route, and remember that the secret entrance is underneath the mushroom, not inside the silo. It’s an easy spot to walk past when you’re busy fighting everything else on the map.
