Core Keeper Urschleim Boss Fight Guide

Urschleim is a tough opponent found in The Passage biome in Core Keeper. A secret boss, you can randomly encounter it while exploring the biome. With the ability to inflict thousands of damage at once, this is how to survive and defeat Urschleim in Core Keeper.

How to Unlock Urschleim Boss in Core Keeper

Urschleim is found wandering The Passage and doesn't require any special unlocks to face. You can build the Urschleim Scanner to track its location through the biome, since it rings the whole map.

The Urschleim Scanner is built at a Rift Statue. These are found throughout the region, placed in the middle of Grimy Flooring with columns and lanterns around it. Like other crafting stations it can be attacked to pick it up and bring it back to your base instead of bringing all your resources to the statue in its original location. Once you're at a Rift Statue, the Urschleim Scanner requires: 

• x20 Ancient Gemstone
• x20 Mechanical Part
• x20 Cytoplasm

Even if you don't have it marked on the map, you'll know what Urschleim is approaching by the world shaking rumble that occurs. If you're looking to face it you can move up towards it, heading in a counter clockwise direction to meet it. If you want to avoid Urschleim, it's a best to leave the region through teleportation or running to the Shimmering Frontier. You can head to an edge of the region and hope to doesn't extend to you, otherwise you risk getting run over and killed. 

How to Win Against Urschleim in Core Keeper | Best Boss Fight Strategy

Urschleim is a large mass with three eyes that rolls over everything in its path. If you're there and get overtaken, it can do between 18,000-24,000 damage, instantly killing you. You don't want to get up close and personal until the Urschleim worm pops out, after destroying the three eyes. Before you take it on, though, you're going to want to prepare your equipment and the area you'll be fighting in. 

Preparing Equipment and Supplies

To start, you want to have the strongest ranged weapon you can. Regardless of doing physical damage or magic, destroying the eyes requires shooting from a distance. You also want to look for one that fires quickly. The Stormbringer, crafted at the Rift Statue, fires 5 times a second and has the damage jump to other enemies within a certain radius. It also boosts movement speed, which is extremely important this fight. 

To buff yourself, have potions or food that increases range damage, magic, range attack speed, and movement speed. You want to move fast and shoot fast. Anything that increases health can help if you get attacked by other Passage enemies, but you shouldn't get close enough for Urschleim to do damage. 

Urschleim is immune to being slowed due to slime, slippery status, and radiation damage. The main mass CAN be stunned or slowed due to magic or weapon effects. 

Preparing the Battlefield

The hardest part of Urschleim is not getting stuck on a wall, in front of empty flooring, or on calcified shells. You need to avoid having the slime blob get too close to you, which gets faster the more damage it's taken. Choose a length of The Passage that it appears in and fill in any of the gaps in the floor that you can. I brought stacks of blocks since mining Fossil Blocks is time consuming and needed to fill in large areas. 

If there's a wall in your way, you're going to want to bring the Mining attire and have your pickaxe completely upgraded and reinforced. Being able to make a decent path through the blocks in an obvious spot will help you find it when attacking Urschleim. 

Urschleim Attack

This boss, contrary to all the other bosses in Core Keeper, doesn't actually attack you. It steamrolls you. Whether you're accidently in its path or actively attacking it, getting run over by the massive slime will result in your death. 

Urschleim Battle Strategy

The strategy for tatking down Urschleim is straight forward. Attack the three eyes while maintaining distance from the body and making sure the path behind you is clear of obstructions. When the three eyes "die" the main Urschleim body pops out near the middle eye, attack it with all the damage you have. The mass stops moving so you can use melee attacks. You'll only have a few seconds to get your attacks in. 

When the worm body retreats into the mass, back up and get your ranged damage ready. This is also a good time to up your potions and food, if necessary. 

Repeat this process until the boss is dead. It can take 3-5 rounds to fully die, depending on your damage output. 

Respawning Urschleim

Once you've defeated Urschleim the first time, you'll need to craft an item from a Rift Statue to have it reappear in The Passage. The Primeval Slime Cell requires x40 Cytoplasm and x30 Ancient Gemstone. 

Core Keeper Urschleim Boss Loot

This is all the loot you can potentially get from beating Urschleim in Core Keeper.

Calcified Shell

• Uncommon
• Crafting component

Cytoplasm

• Uncommon
• Crafting component

Desert Ruby

• Epic
• Crafting component

Giant Mitochondrion

• Epic
• Consumable
• +100 max health (only once) 
• Guaranteed drop (first time only)

Jungle Emerald

• Epic
• Crafting component

Ocean Sapphire

• Epic
• Crafting component

Squishy Egg

• Uncommon
• Pet egg

Sulfossil Boots

• Epic
• +54 max health
• +31 armor
• +15.8% damage
• 2 set: +25% explosives damage
• 3 set: Deals 74 damage to all nearby enemies when taking damage

Sulfossil Cuirass

• Epic
• +57 max health
• +31 armor
• +14.7% damage
• 2 set: +25% explosives damage
• 3 set: Deals 74 damage to all nearby enemies when taking damage

Sulfossil Helmet

• Epic
• +42 max health
• +22 armor
• +10.5% damage
• 2 set: +25% explosives damage
• 3 set: Deals 74 damage to all nearby enemies when taking damage

Sulfur Bomb

• Uncommon
• 1143-1395 explosive damage

Urschleim's Chest

• 36 slots (12x3)
• Guaranteed drop

Urschleim Figurine

• Epic
• Decoration

That's how to prepare for and defeat The Passage boss, Urschleim, in Core Keeper.