Core Keeper Bosses Guide: Here Comes The Slayer Of Slimes!

The subterranean world of Core Keeper is filled with mystery, intrigue, and dangerous monsters lurk around every corner.

The most formidable of all are the bosses, many of which require specific gear or strategies to beat. Core Keeper is a punishing experience for newcomers as it doesn’t teach you how to play. Unless you know how to approach these difficult battles, you can easily get stuck for hours without progressing.

There are nine mandatory bosses in Core Keeper, and in this guide, I’ll show you how to beat all of them. Let’s begin!

Bottom Line Up Front

Bosses in Core Keeper all mark a significant milestone on your journey through the game. They aren’t designed to be rushed, and gathering all the required items for the battles will take multiple hours, even if you’re an experienced player.

The later bosses are much more challenging and have a punishing entry barrier, as you need to craft expensive items before they appear. Because of this, it’s worth over-preparing for each encounter.

A Couple of Useful Tricks

Before we dive into specific strategies for every boss, there are a few things you may not know that will help with your battles moving forward.

Mark Boss Locations on Your Map

After you’ve beaten the first boss, mark where its summoning rune is on your map, as it will be handy later. You can do this on the map by pressing the mouse wheel in. Doing this for every boss battle is good practice if you want to farm them for their unique drops.

How do I Find Bosses

Besides Glurch the Abominous Mass and Ghorm the Devourer, the best way to find bosses is with a Scanner.

Scanners can be crafted from various Vendors, and they mark boss locations on your map. You can stumble across these areas by accident, but considering how huge the map gets the further you wander from the Core, it’s unlikely. Scanners cost Ancient Coins, and you can get this currency by selling items to Vendors. Any item in your inventory marked ‘valuable’ has no purpose but to be sold.

Build a Poison Slime Farm

After the 3rd main boss fight, you’ll notice that future bosses and general enemies hit much harder than they ever did before. The best way to quickly recover health is with Healing Potions, which can be tricky to make in large quantities as Poison Slimes are a key ingredient.

Making a Slime Farm is a great way to passively get lots of Poison Slimes. They can be simple, like mine in the picture above.

As long as the area is dark, Slimes will spawn, matching the color of any slime on the ground. If you farm some poison slime (shovel it off the floor) and place Spike Traps nearby, Poison Slimes will spawn and skewer themselves so you can collect the rewards.

Use my layout as an example. The Remedaisy Necklace completely negates poison and is a rare drop from Poison Slimes. If you make a farm, you won’t have to wait long to get this powerful item.

Bring a Bed to Boss Battles

It’s not a foolproof strategy, but if you rest in a bed near a boss fight, you’ll respawn there. Bosses regain their health once you die and respawn at your base, but you can sometimes stop this if you sleep nearby. This won’t work all the time, but it is worth trying if a particular boss is causing you problems.

Reinforce Your Gear

Reinforcing your gear at the Salvage Station is great as it dramatically increases durability. It also increases your item’s stats and is a quick and cheap way to strengthen your build. Reinforcing is useful no matter where you are in the game, and I recommend doing it whenever possible.

The Bosses

In this section, I’ll explain how to beat every boss in the order you’ll likely encounter them. I’ll also suggest appropriate gear. Your equipment choice won’t matter much for the earlier bosses, but it’s crucial later.

Glurch the Abominous Mass

Glurch is the first wall new players face in Core Keeper, but for many, the hardest part will be tracking him down in the first place.

Glurch will spawn close to the Core, but his lair can be in any direction. You can tell when you’re close as the floor will periodically rumble. Unlike most later bosses, there’s no Scanner to track this boss down, so you’ll have to explore until you stumble across Glurch naturally.

Recommended Gear

• Head – Bronze Helm
• Chest – Bronze Breastplate
• Legs – Bronze Pants
• Offhand – Swift Feather (Optional)
• Weapon – Wooden Bow

The first boss hits surprisingly hard, so a full suit of Bronze Armor is essential for this fight. Glurch is a simple creature and repeatedly tries to crush you.

The best strategy is to kite him around the arena while shooting. This is easier said than done, as the lair is covered in slime, which slows you down. Try and keep your distance at all costs and attack from afar. You can use a Bronze Sword, but as Glurch hurts so much, it’s risky.

If you’ve stumbled across any Locked Chests, there’s a slim chance you’ll find a Flintlock Musket. If you’re lucky enough to have one of these, use it to make short work of the boss. Another item you may find in chests is the Swift Feather. This lets you dash around the arena and makes the slime much easier to deal with.

To keep your speed up during this fight, I recommend cooking some Mushy Pepper Wraps (Mushroom + Bomb Pepper). These give a 21% Movement Speed buff which can be the difference between life and death.

When Glurch’s health is low, he will enter an enraged state which gives him a dramatic speed increase. You shouldn’t need to adjust your strategy here, just focus on ensuring you don’t get trapped against the scenery, and you should comfortably beat this encounter.

Ghorm the Devourer

Ghorm the Devourer is the most unique boss in Core Keeper and thunders around the underworld, leaving a massive slimy canyon in its wake. Once you travel far enough in any direction, you’re guaranteed to run into its trail. Now all you have to do is kill it!

Recommended Gear

• Head – Bronze Helm
• Chest – Bronze Breastplate
• Legs – Bronze Pants
• Offhand – Swift Feather
• Weapon – Any

If you attack Ghorm with a conventional weapon, it will have you for breakfast. It’s as simple as that. The best strategy to defeat the boss is to pave its path in Spike Traps. Each Trap costs 2 Tin Bars and can be crafted on a Tin Workbench.

As for how many you need, it depends on how many players are in your game. For a team of two, I needed about 250 Traps. This may sound excessive, but Ghorm is obnoxiously hard to beat any other way.

When your traps are ready, wait until Ghorm goes past before planting them. It takes Ghorm roughly 5 minutes to make a complete circuit, giving you plenty of time to cover the canyon floor in Traps.

The boss will hit every Spike Trap that’s not touching the walls so you can spread them wide. Once your traps are set, stay a safe distance away and be ready to deal the killing blow if Ghorm somehow survives.

The only thing to note with this strategy is your traps will be destroyed when Ghorm runs over them. If you don’t do enough damage, the boss will have full health when it repeats the circuit, and all of that Tin you gathered for the Traps will go to waste. Therefore, it’s better to over-prepare for this fight and bring more Traps than you need.

The Hive Mother

The Hive Mother is the first wall you’ll likely face in Core Keeper. There are a few ways to approach the fight, but this strategy is simple, fairly quick, and doesn’t require much setup.

Recommended Gear

• Head – Iron Helm
• Chest – Iron Breastplate
• Legs – Iron Pants
• Offhand – Swift Feather
• Weapon – Any

After Ghorm, you definitely understand the power of Spike Traps. You’re going to use them again, but for this battle, we will need to get our hands dirty.

The Hive Mother won’t attack until you do, so start by placing a walkway of Spike Traps around the boss. These don’t hurt the player, so the strategy is to run around this path of Spikes while dealing damage with the weapon of your choice.

You’ll be close enough to use melee attacks, but I still prefer ranged weapons for boss battles. For this fight, I used the Flintlock Musket. If you’d like to use a melee, the Battle Axe is excellent and can be found in locked Iron Chests.

The walkway you’ve constructed isn’t to hurt the boss; it’s to damage the smaller enemies that spawn during the fight. If too many show up, you’ll sometimes need to deal with them instead of the boss, but the Spikes will do the heavy lifting.

Aside from the enemies that appear, Hive Mother only has one attack you need to worry about. The boss will shoot acid projectiles into the air that do a ton of damage if they hit you. Fortunately, their landing zone is displayed with a bright red marker, and as long as you’re nowhere near when it lands, you’ll be fine.

One item you’ll definitely want for this fight is food that grants immunity to Acid. Anything with a Green Blister Fish as one of the ingredients will grant Acid immunity for 5 minutes making the whole biome much less scary. You can catch these fish in the Clay Caves Biome.

Azeos the Sky Titan

Azeos is a majestic bird that soars over his arena until you place a Large Shiny Glimmering Object to bring him down.

This object is consumed upon use, even if you lose the battle. Azeos is quite different from any other boss you’ve faced so far, and there are two strategies you can use. One is the intended way, and the other is an exploit.

Recommended Gear

• Head – Scarlet Helm
• Chest – Scarlet Breastplate
• Legs – Scarlet Pants
• Offhand – Swift Feather
• Weapon – Any

The first thing you should do is prepare the arena. Azeos’s lair always has a chasm surrounding it, and the fight is much easier if you construct a few bridges across. I filled the entire area with wooden platforms, but it’s not strictly necessary.

You can use any weapon you feel comfortable with, but a ranged weapon like the Flintlock Musket or Blowpipe is excellent for this encounter.

Once you’ve placed the Large Shiny Glimmering Object, Azeos will appear in that spot and immediately start attacking. Azeos summons blue fiery laser beams, which look intimidating but are predictable and follow a pattern. Once you learn those patterns, you can defeat this boss without getting hit.

Azeos will periodically summon blue crystals to the battlefield. While these are active, they will restore the boss’s health. These crystals grant so much healing you should destroy them as soon as they appear. The fastest way to do this is with a Pickaxe.

These crystals can sometimes appear outside the arena, which is why you need those bridges. Once you memorize the laser patterns, this feathered menace goes down quickly.

The Cheese Strategy

Create a small square of Spike Traps 2 tiles wide around four empty tiles where you will place the Large Shiny Glimmering Object.

Once the Traps are set, you need to stand Exactly 18 tiles away from where the boss will spawn. The easiest way to see these tiles is to mark them diagonally with tiles. Next, you must eat an item to increase your movement speed.

Any Pepper Wraps are fine for this. Eat a Wrap, spawn Azeos, and immediately run to your tile. If you don’t have some sort of speed buff, Azeos will aggro on you before you get to the tile, and the trick won’t work.

This puts you in a unique position where Azeos won’t attack you but won’t regain health either. All you need to do is wait until Azeos succumbs to the Traps and collect your rewards.

Be warned that this strategy is very slow and takes over 5 minutes if you’re playing solo. It takes even longer if you’re in a group. Full credit goes to Serroh on YouTube for showcasing this trick.

Ivy the Poisonous Mass

This battle isn’t too different from the fight against Glurch, the Abominous Mass. The arena is much more hostile, so you can’t just rely on your combat skills if you want to win.

Recommended Gear

• Head – Scarlet Helm
• Chest – Scarlet Breastplate
• Legs – Scarlet Pants
• Offhand – Azeos’ Dash Feather
• Necklace – Remedaisy Necklace
• Rings – Gold Crystal Ring x2
• Weapon – Fireball Staff

Ivy, the Poisonous Mass, acts similarly to Glurch and will try to jump on you to deal damage. Ivy sometimes stops jumping, and poison blobs will rain down on the arena. It’s a scary-looking attack, but you’ll be fine if you stay out of the red circles that appear.

The biggest issue you’ll have in this fight is that the ground is covered in poisonous slime, which will drain your health. Because of this, I strongly recommend wearing a Remedaisy Necklace as it completely negates poison damage.

There’s a case to be made for using the Larva set (Grub Egg Necklace + Larva Ring), as it negates the speed debuff from the slime on the ground. I absolutely recommend Poison Immunity over this combo, as you can still move fast enough with either a Swift Feather or Azeos’ Dash Feather.

Ivy, the Poisonous Mass, can spawn in areas covered in obstacles like holes. You can fill these in during the fight for more mobility.

When Ivy enters its enraged state, it attacks faster, but the same strategy of kiting it around the map will still work. As I used a ranged weapon for this fight, Keen Potions were helpful as they increased ranged damage for a short while.

King Slime

Although technically optional, King Slime is an easy kill compared to Ivy the Poisonous Mass and drops a couple of items that will aid you on your journey into the next area, the Sunken Sea.

To summon King Slime, you must place a Crown Summoning Idol on Glurch’s Rune (the circle on the floor in his lair). Crown Summoning Idols have a 0.24% chance to drop whenever you kill any slime.

Recommended Gear

• Head – Scarlet Helm
• Chest – Scarlet Breastplate
• Legs – Scarlet Pants
• Offhand – Azeos’ Dash Feather
• Rings – Gold Crystal Ring x2
• Weapon – Fireball Staff

King Slime is functionally identical to Glurch, albeit with much more health. This boss really hurts if he lands on you hence the strong Armor recommendation. If you’ve beaten Ivy, you should have Scarlet gear readily available, but you can use anything suitable for this part of the game. As King Slime does so much damage, engaging from a distance is safest.

The Fireball Staff is fantastic and can be found in Iron Chests. If you don’t have one, the Flintlock Musket or Grubzooka are both solid options. I recommend using a pair of Gold Crystal Rings to boost your ranged damage, but plenty of items do the same thing. You can craft these with a Jewelry Workbench.

Royal Gel and The King Slime Crown are guaranteed drops from this fight, and equipping both stops any slime in the game from attacking you. Oddly enough, this also works on every enemy in the Sunken Sea biome, making the area a cakewalk.

As you’ll be traveling deep into this zone to reach the next boss, defeating King Slime is well worth the cost of admission.

Omoroth, the Sea Titan

Omoroth marks a massive spike in difficulty and serves as a painful DPS check. If you can’t consistently deal enough damage, you’ll be overwhelmed by Omoroth’s tentacle attacks. This fight is tough, and the ‘Expert Lure’ required to summon it is incredibly expensive.

To craft the Expert Lure, you need the following:

• Purple Bait x1
• Spicy Bait x30
• Sweet Bait x30
• Glowing Bait x30
• Octarine Bar x30
• Ancient Gemstone x10

The Lure is consumed upon use, whether you win or lose. The baits aren’t hard to make but are a pain if you neglect your farming duties. Octarine Ore for the bars appears in the Sunken Sea area, so I recommend beating King Slime before you attempt the battle.

Recommended Gear

• Head – Octarine Helm
• Chest – Ivy’s Thorn Harness
• Legs – Ivy’s Pants
• Offhand – Octarine Shield (Blue Leather Tome if you have it!)
• Rings – Polished Gold Crystal Ring x2
• Weapon – Fireball Staff or any other appropriate ranged weapon.
• Other – Keen Potions and Guardian’s Potions.

The Ivy’s set is earned from defeating Ivy the Poisonous Mass, and it’s great because it gives extra Critical Hit Damage. The Rings and Keen Potion boost ranged damage, and Guardian’s Potion reduces damage from Bosses.

The Omoroth fight isn’t complicated, but it’s difficult because a lot is happening, and you’ll need to craft a boat to fight from. Boats in Core Keeper handle surprisingly well, but there’s a learning curve as they aren’t as snappy as moving on land.

To start the fight, fish in any of the whirlpools with the Expert Lure in your Offhand. The Lure will be consumed as soon as the battle begins, but you should have enough time to put the Octarine Shield in the slot before you get attacked.

Omoroth will move between whirlpools and throws projectiles at the player. These hurt, but the bigger problem is the tentacles.

These can get out of control if you’re not dealing enough damage and put you in a situation where winning becomes impossible. You’ll quickly learn Omoroth’s attacks, and the best way to win is to keep your distance and throw everything you can at it.

This is a long battle, as Omoroth has the highest health pool in the game. You can ‘cheese’ the fight similarly to Azeos by staying just outside its aggro range, but this is much harder to set up because the arena is in the water. You’ll lose an Expert Lure every time you attempt this, so only try this method as a last resort.

Morpha, the Aquatic Mass

You’re probably quite good at fighting these slime bosses by now! Morpha can be found in the Sunken Sea and, while much easier than Omoroth, can still be a threat if you get complacent.

Recommended Gear

• Head – Octarine Helm
• Chest – Octarine Breastplate
• Legs – Octarine Pants
• Offhand – Toxic Defender Shield
• Necklace – Mold Vein Necklace (for ranged weapons)
• Rings – Polished Gold Crystal Ring x2 (for ranged weapons)
• Weapon – Bubble Gun

The big problem with this boss fight is the blue slime all over the arena. It doesn’t hurt, but you’ll slip and slide all over it, making positioning difficult.

Morpha’s slam attack hurts a lot, just like the other slime bosses. Since we can’t avoid the attacks so easily, we can block them instead with a Shield. The Toxic Defender Shield is another valuable item in Ivy’s loot pool. Hold Space to stop most of the incoming damage when you’re about to get hit.

Any weapon for this late part of the game is fine, but melee doesn’t really work, as you have such poor movement. Other than the blue slime on the ground, you’ve dealt with this style of fight many times before.

Ra-Akar the Sand Titan

Ra-Akar is a tough customer but nowhere near as bad as the Sea Titan with the appropriate gear. Getting said gear will take some time, but with the new Galaxite ore in this area, you can make some mighty new toys. To spawn Ra-Akar the Sand Titan, you need a Thumper. This can be crafted at the Ancient Hologram Pod and requires the following:

• Fiber x50
• Plank x50
• Scarlet Bar x30
• Galaxite Bar x30
• Mechanical Part x10
• Ancient Gemstone x20

As with the other boss summoning items, the Thumper is single-use and is consumed regardless of whether you win the fight.

Recommended Gear

• Head – Galaxite Helm
• Chest – Galaxite Breastplate
• Legs – Galaxite Pants
• Offhand – Azeos’ Dash Feather
• Necklace – Mold Vein Necklace
• Rings – Polished Gold Crystal Ring x2
• Weapon – Galaxite Chakram or Bubble Gun

You’ll have access to some fantastic gear at this point in the game. The Galaxite set is superb and easy to craft, but I do prefer two pieces of the Ivy’s Set for ranged damage. The downside is it’s not as protective, but you should kill the boss faster.

The Galaxite Chakram is an insanely strong ranged weapon and only costs 22 Galaxite Bars to make. It’s got a fast fire rate and zero pushback when you shoot; honestly, it’s so good you’ll struggle to go back to anything less.

Ra-Akar has several nasty attacks. The most dangerous is a stream of 6 slow-moving projectiles that speed up as they approach the player. These shots follow you no matter what you do, and the best way to avoid them is to run in a small circle when they are close. You can run them into stone pillars as a backup strategy.

Dodging the projectiles is tough because Ra-Akar frequently spawns reinforcements in the form of bugs. These relentlessly pursue the player; just like the Omoroth fight, you must deal with them before they become a big problem.

The boss infrequently stops to attack with sand whirlpools, and they aren’t too hard to avoid, but they make ranged weapons far more reliable than melee. As Ra-Akar deals contact damage and is quite mobile, close-range combat is out of the question unless you’re already comfortable with the fight.

Core Keeper Bosses Guide: FAQs

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Anthony Yates

Anthony is a content writer who is also a competitive gamer. He plays and streams a variety of retro games. He spent hours exploring the indie gaming world and learning its mechanics. He knows how to complete challenges, and creates strategies for different playthroughs. In his spare time, he enjoys cosplaying and creating assets for events and Cons.

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