Pikmin 4 Cavern for a King: Complete 20-Sublevel Walkthrough and Boss Guide

What Is the Cavern for a King?

The Cavern for a King is the final cave in Pikmin 4, tucked away at the very north of the Primordial Thicket. With a staggering twenty sublevels, it holds the record for the longest cave in the entire series, and it houses the game's final boss: the Ancient Sirehound, with Louie riding on its back.

Much like the Hole of Heroes from Pikmin 2, this cave is essentially a boss rush. Nearly every sublevel pits you against a returning boss or a brand-new threat, including fresh faces like the Toxstool and the Titan Blowhog. In total, the cave contains 2,935 Sparklium worth of treasure, making it well worth the effort to fully explore.

How to Unlock the Cave

You cannot simply walk up to the entrance. When you first reach the northern edge of the Primordial Thicket, a massive boulder blocks the way down. The boulder disappears once you have rescued the castaway Nelle and spoken with her at the Rescue Command Post. After that conversation, the rock is inexplicably gone and the cave entrance is open for business.

A few preparation tips before you descend:

• Bring a balanced squad, with extra Purple, Rock, Ice, and White Pikmin as you get deeper.
• Stock up on Ultra-Spicy and Ultra-Bitter Sprays if you have them.
• Make sure Oatchi is leveled up, since his Rush and Doggy-Paddle abilities carry many of the fights.
• Set aside plenty of time. Twenty sublevels with a boss on almost every floor is the single longest expedition in the game.

Sublevel-by-Sublevel Walkthrough

Use this table as a quick reference for every floor, then read the detailed notes below for the trickiest fights.

Key Fights Explained

• Sublevel 1 (Toxstool): This floor sets the tone. Poison enemies and sticky mold cover the area, and the Toxstool revives fallen foes while replenishing the mold. Target the Toxstool first using Oatchi's Rush, freeze it with Ice Pikmin, then mop up the rest.
• Sublevels 3 and 5 (Triple threats): Three Burrowing Snagrets appear together for the first time since the original Pikmin, and three Emperor Bulblaxes follow shortly after. You must defeat every boss on these floors to proceed, and the Bulblaxes' roars can wake each other up, so fight them one at a time using Ultra-Spicy Sprays and Oatchi's Rush.
• Sublevel 10 (Smoky Progg): The infamous Smoky Progg returns after more than two decades. It hatches shortly after you enter, so rush it immediately with Oatchi and use Bomb Rocks if needed. Stay away from its gloom at all costs.
• Sublevel 16 (Two Waterwraiths): A nod to Pikmin 2's Bully Den, this floor sends two Waterwraiths after you. Stock up on Purple Pikmin from the Violet Candypop Buds, then engage one at a time. Knock out one's rollers before the second arrives so you never fight both at once.
• Sublevel 18 (Sovereign Bulblax): The original game's final boss caps off the Bulborb gauntlet. Its jump attack deforms the terrain and can create small pools of water. Rush with Oatchi, throw Bomb Rocks like you did back in the day, or lean on Purple and Rock Pikmin for heavy damage.
• Sublevel 20 (Ancient Sirehound): Louie hops onto a giant dog, and the final battle begins. Beat the boss, collect the Gift of Friendship, and rescue Louie. You will exit the cave immediately, then choose to finish the day in the Primordial Thicket or end it. Ending the day triggers the game's closing cutscene.

Rest Levels and Preparation Floors

Not every floor wants you dead. Sublevel 6 is a safe haven with Honeywisps that provide nectar and possibly sprays, plus Candypop Buds to rebalance your squad and a surface exit if things went badly. Sublevel 12 offers another exit point, two Violet Candypop Buds, and nectar. Sublevel 19 is your last stop before the finale: seven Honeywisps supply nectar, Candypop Buds let you convert Pikmin for the final fight, and Louie's scattered snacks are worth grabbing. Take your time here and leap down the hole only when you feel ready.

Practical Tips for Surviving All 20 Floors

• Elemental matchups matter. Ice Pikmin freeze water, poison mold hazards, and several bosses. Purple Pikmin crush tough bosses and weigh down charging enemies like the Crusted Rumpup. Rock Pikmin minimize losses against rolling threats.
• Abuse Oatchi's Rush. It deletes small enemies, staggers bosses, and often ends fights before they begin.
• Mind the environment. Sublevel 4's Arctic Cannon Beetle guards a long twisting hallway with snowballs that pin you against the walls; hide in alcoves and clear the Dwarf Orange Bulborbs hiding in them. On sublevel 15, wait for the Baldy Long Legs to step into the water pit, freeze it with Ice Pikmin, and attack while it is stuck.
• Skip fights when possible. On sublevel 7, if you can live without the S.S. Peppermint and S.S. Berry, a well-timed Oatchi jump over the gate lets you bypass the Titan and Blizzarding Blowhogs entirely.
• Watch for Candypop Bud limits. The game never lets you control more than six Pikmin types at once (seven counting Glow Pikmin). A bud that would give you a seventh type converts to Ice instead, or White or Purple depending on your squad. This shows up most often on sublevel 19.

Fun Facts About the Cave

• At twenty sublevels, the Cavern for a King beats Pikmin 2's Hole of Heroes (the previous record holder) by five floors, and Pikmin 4's second-longest cave, the Kingdom of Beasts, by a full fourteen.
• The cave's name is likely a reference to Louie's treasure title, "King of Bugs."
• A known glitch on the Smoky Progg floor can cause it to drop multiple Wayward Moons, potentially pushing your cave completion past 100 percent.
• Louie's Voyage Log entry for the cave reads: "Finally tamed that huge dog thing. I'm gonna lie low for a while in its den. It's really deep, and there are plenty of snacks. The others will give up and go home."

FAQ

How many sublevels does the Cavern for a King have?

Twenty, the most of any cave in any Pikmin game. Almost every floor except the rest levels features at least one boss encounter.

How do you unlock the Cavern for a King?

Rescue Nelle, then talk to her at the Rescue Command Post in the Primordial Thicket. The massive boulder blocking the cave entrance at the north of the area will be gone afterward.

Who is the final boss of Pikmin 4?

The Ancient Sirehound on sublevel 20, with Louie riding on its back. Defeating it and rescuing Louie triggers the ending sequence after the day ends.

What is the best squad to bring into the cave?

A mix of Purple, Rock, Ice, White, and Blue Pikmin covers nearly every encounter, with Candypop Buds on rest floors letting you adjust. Bring Oatchi at a high level and as many sprays and Bomb Rocks as you can carry.

Is the cave required to beat the game?

Yes. The Ancient Sirehound fight is the game's final boss, so completing this cave is how you reach Pikmin 4's ending.

Details in this guide are drawn from the Pikmin Wiki's Cavern for a King page on Fandom, which documents each sublevel's enemies, treasures, and strategies in depth.