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Passive outer being protecting an aggressive, explosive core.

Ghastly, eerie creature made out of thick liquid. You can peer right through them, and can't see where they keep their thoughts. I don't trust them at all. Keep away.

Oomas are enemies in Hollow Knight. They have a pulsing orange core which can propel itself through the air if the outer shell is damaged.[1] Monomon the Teacher has an unknown connection to them.[2]

Behaviour and Tactics

Floats up and down in place in a set pattern.

Its body bursts when hit, revealing its volatile orange core. After an extremely brief moment, the core homes in on the Knight, exploding on contact with the Knight, a wall, or an attack and dealing 2 Masks of damage to the Knight and 9999 damage to enemies. Ooma explosions only deal 50-150 damage to Uumuu when fought in Godmaster content Godhome.[Note 1]

The core is tricky to avoid due to its travel speed, so it is advised to mainly avoid attacking Ooma when possible; they are otherwise passive.

A direct hit from a Vengeful Spirit/Shade Soul projectile continues pushing the explosive core along its path, often until it hits a wall and explodes. This is the safest way to destroy an Ooma but requires SOUL to be spent.

Another way to destroy Oomas without dealing with the exploding core is acid. If an Ooma is pushed into acid (via a Nail strike from above), the core is harmlessly destroyed along with the rest of the Ooma. Unfortunately, this method of killing does not allow Geo to be collected from the kill.

The Grimm Troupe content Weaversong, Grimm Troupe content Dreamshield, Glowing Womb, Grimm Troupe content Grimmchild, and Defender's Crest Charms attack them, and the volatile core is still launched at the Knight, so it is not recommended to wear these Charms while in Fog Canyon.

Dream Nail Dialogue

  • ...MONOMON...


They are found in large numbers in almost every area of Fog Canyon.



  • Shadow Dashing through an Ooma while using the Sharp Shadow Charm causes its explosive core to always go to the right, independently of the direction dashed. Whether this is intentional or a bug in the in-game physics is unknown. The same happens if they are hit by Grimm Troupe content Dreamshield.
  • The explosive core cannot be damaged by the Spore Shroom or Defender's Crest Charms.


  1. The explosion lasts 0.5 seconds and constantly deals 50 damage, but Uumuu has 0.15 seconds of invulnerability when its shield breaks and each time it takes damage, making the total damage variable.


  1. Wanderer's Journal, p. 134.
  2. Ooma Dream Nail dialogue: "...MONOMON..."
Hollow Knight Enemy Compendium
EnemiesBossesHealth ValuesColosseum of FoolsGodmaster content Hall of GodsGodmaster content Pantheons
Main Game
Forgotten Crossroads CrawlidVengeflyVengefly KingGruzzerGruz MotherTiktikAspid HunterAspid MotherAspid HatchlingGoamWandering HuskHusk HornheadLeaping HuskHusk BullyHusk WarriorHusk GuardEntombed HuskFalse Knight (Failed Champion) • MaggotMenderbugLifeseedBaldurElder Baldur
Greenpath MosscreepMossflyMosskinVolatile MosskinFool EaterSquitObbleGulkaMaskflyMoss ChargerMassive Moss ChargerMoss KnightMossy VagabondDurandooDurandaAluba
Fog Canyon Charged LumaflyUomaOomaUumuu
Fungal Wastes AmbloomFunglingFungoonSporgFungified HuskShrumelingShrumal WarriorShrumal OgreMantis YouthMantis WarriorMantis Lords
City of Tears Husk SentryHeavy SentryWinged SentryLance SentryMistakeFollySoul TwisterSoul WarriorSoul Master (Tyrant) • Husk DandyCowardly HuskGluttonous HuskGorgeous HuskGreat Husk SentryWatcher KnightCollector
Royal Waterways BelflyPilflipHwurmpBluggsacDung DefenderFlukefeyFlukemonFlukemarm
Crystal Peak ShardmiteGlimbackCrystal HunterCrystal CrawlerHusk MinerCrystallised HuskCrystal Guardian (Enraged)
Infected Crossroads Furious VengeflyVolatile GruzzerViolent HuskSlobbering Husk
Deepnest DirtcarverCarver HatcherGarpedeCorpse CreeperDeeplingDeephunterLittle WeaverStalking DevoutNosk
Ancient Basin Shadow CreeperLesser MawlekMawlurkBrooding MawlekLightseedInfected BalloonBroken Vessel (Lost Kin)
Kingdom's Edge BooflyPrimal AspidHopperGreat HopperGrub MimicHivelingHive SoldierHive GuardianHusk Hive
Queen's Gardens Spiny HuskLoodleMantis PetraMantis TraitorTraitor Lord
Colosseum of Fools Sharp BaldurArmoured SquitBattle ObbleOblobblesShielded FoolSturdy FoolWinged FoolHeavy FoolDeath LoodleVolt TwisterZoteGod Tamer
Warrior Dreams XeroGorbElder HuMarmuNo EyesGalienMarkoth
White Palace WingmouldRoyal RetainerKingsmouldSiblingVoid Tendrils
Story Bosses Hornet (ProtectorSentinel) • Hollow KnightRadianceShadeHunter's Mark
Content packs
Hidden Dreams content Hidden Dreams Grey Prince ZoteWinged ZotelingHopping ZotelingVolatile ZotelingWhite Defender
Grimm Troupe content The Grimm Troupe Grimmkin NoviceGrimmkin MasterGrimmkin NightmareGrimmNightmare KingSeal of Binding
Lifeblood content Lifeblood Hive Knight
Godmaster content Godmaster FlukemungaPale LurkerSisters of BattleWinged NoskNailmasters Oro & MatoPaintmaster SheoGreat Nailsage SlyPure VesselAbsolute RadianceVoid IdolWeathered Mask