Uumuu

"Intelligent being that guards the inner chamber of the Teacher's Archives. The canyon below us, the one thick with fog and crackling with strange energy... a Hunter can lose their senses down there. Be careful... strange and unnatural things lurk there."

Uumuu is a main boss in Hollow Knight. It guards Monomon the Teacher, one of the Dreamers.

Lore Uumuu is an intelligent yet infected being similar to the Uomas and Oomas infesting the Fog Canyon. It defends Monomon's chamber at the heart of the Teacher's Archives.

In-game events Uumuu appears from the acid pool in the room preceding the inner chamber once the Knight reaches it. During the fight, Quirrel intervenes to strike Uumuu with his nail and break its gelatinous defence to expose its core. Once defeated, the Infection bursts out of Uumuu before it explodes.

When fought in Godhome, Quirrel is not present. Instead, Uumuu summons Oomas to help it, but they can be used to break its defence.

Behaviour and Tactics
Uumuu floats around the room and uses one of two attacks:
 * Burst: Uumuu fills the arena with small bursts of lightning. Each lightning burst lasts for about one second. The lightning bursts appear in random spaces throughout the arena, but there are some safe areas for the Knight to stand. The lightning bursts become dangerous at different times. The entire attack lasts for about two and a half seconds.
 * Chase: Uumuu creates a small burst of lightning where the Knight is, similarly to Volt Twisters. Uumuu continues to create a new small burst of lightning every second for about six seconds. Each burst persists for about two seconds. Each new burst appears where the Knight is, so constant movement is necessary.
 * Hover: While not attacking, Uumuu hovers around the arena, slowly chasing The Knight.

When initiating the fight, Uumuu can deal damage when it rises up from its resting spot within the acid.

Uumuu cannot be harmed normally, as its vulnerable core is protected by a membrane that deflects the Knight's attacks and shields it from Spells. However, after dodging attacks for a short time Quirrel appears to help the Knight, leaping around the battlefield and occasionally popping Uumuu's shield. This deflates Uumuu, leaving it open to attacks for about 5 seconds.

Although Uumuu may only have two attacks, they are both quite hard to dodge, and their pattern leaves few opportunities for healing. In addition, Uumuu's erratic movements and the very sparse opportunities for hitting it compared to its health pool result in a very drawn-out battle.

Get in as many hits as possible when Uumuu's shield is popped, and be prepared to dodge an attack right after. In desperate times, this can be an opportunity to heal instead. Avoid jumping in the water below a platform in the arena, as this greatly slows movement.

As with most boss fights, Quick Focus is highly recommended. SOUL-generating charms like Soul Catcher/Soul Eater, Kingsoul, and Grubsong are also very important in this fight, as chances to hit Uumuu and consequently to gather the SOUL needed for healing are quite rare. Great Slash and a Pure Nail are recommended in order to make short work of Uumuu.

Uumuu can be completely killed by using the Abyss Shriek three times with Shaman Stone, allowing it to be beaten in one cycle, given that enough SOUL has been gathered before the fight.

Using the Dream Nail on Uumuu is a good way to gain large amounts of SOUL, but it can be difficult to avoid getting damaged. Equipping the Dream Wielder charm for this fight makes it easier to use the Dream Nail.

While in Godhome in the Pantheon or Hall of Gods, Quirrel is no longer at the Knight's side to break Uumuu's protective membrane. However, Uumuu does gain a new attack that can be turned against it. Uumuu is also slower in this incarnation.

Uumuu has all the same attacks as its regular form with one new one used to make it vulnerable:
 * Summon: Uumuu emits a screech and summons two Oomas that slowly float up until they disappear from the top of the screen. The Oomas themselves pass through all platforms, but their cores, once exposed, explode if they are intercepted with a platform. Getting these Oomas' explosive cores to collide with Uumuu breaks its shield while additionally dealing 100 damage to Uumuu. Uumuu also becomes invulnerable to the Oomas while screeching to summon more.

There are a couple of methods of making Uumuu vulnerable:
 * Have the Knight at an angle where the Ooma is right between them and Uumuu, then strike the Ooma in Uumuu's direction.
 * If the Ooma is in close proximity to Uumuu or even behind/directly inside it, use a ranged spell such as Vengeful Spirit/Shade Soul to trigger the Ooma.
 * The trickiest method is to dispatch the Ooma while being between it and Uumuu, then kite out the homing explosive core so that it is guided into Uumuu.

Otherwise, the fight stays relatively the same with the same dodging tactics.

Location
Uumuu is located in the centre of the Teacher's Archives.

Trivia

 * The Uumuu fight is one of four fights in the game where an NPC aids the Knight; the other three are Traitor Lord with Cloth, the Hollow Knight with Hornet and the Radiance with the aid of The Hollow Knight.
 * Nail-bouncing on top of Uumuu, while it is still invulnerable, launches the Knight a higher distance than usual.

References

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