Hydruka
Scorpion Rahi of Mahri Nui
Aquatic scorpion-like Rahi domesticated by the Matoran of Mahri Nui to harvest Airweed, and the natural prototype for the Air Launcher weapon.

The Hydruka was an aquatic scorpion-like RahiRahiThe Rahi were the biomechanical wildlife of the Matoran Universe, built largely by the Brotherhood of Makuta, ranging from background fauna to engineered war beasts. species native to the PitThe PitThe Order of Mata Nui's maximum-security underwater prison where the Barraki warlords were held until catastrophe broke their chains., created by the MakutaMakuta (Species)Shadowy Antidermis beings and the Brotherhood's elite, Makuta commanded darkness and shaped the Matoran Universe's fate. and later domesticated by the MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body. of Mahri NuiMahri NuiA matoran settlement that sank, survived, and was ultimately crushed beneath Voya Nui, leaving behind one of Bionicle's most poignant lost civilizations. as harvesters of AirweedAirweedThe underwater plant of the Fields of Air whose bubbles let the Matoran of Mahri Nui breathe beneath the sea.. The species was the natural source of the Solidified Air Bubbles later replicated by the MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body.-built Air LauncherAir LauncherThe Air Launcher is a defense weapon used by the Matoran of Mahri Nui that shoots air bubbles. The device is no longer in use. weapon. (BIONICLE Legends 6: City of the Lost; BIONICLE: Encyclopedia Updated)
Origin and natural traits#

The Hydruka was created by the MakutaMakuta (Species)Shadowy Antidermis beings and the Brotherhood's elite, Makuta commanded darkness and shaped the Matoran Universe's fate. from viruses and liquid ProtodermisProtodermisThe engineered substance building the Matoran Universe, protodermis exists in countless refined states from mundane metal to diamond-hard crystal to the destruction-or-transformation force of energized form., like other engineered RahiRahiThe Rahi were the biomechanical wildlife of the Matoran Universe, built largely by the Brotherhood of Makuta, ranging from background fauna to engineered war beasts.. It took the form of an aquatic scorpion-like creature, and was sensitive, irritable and temperamental, which made handling it a skill in itself. (BIONICLE: Makuta's Guide to the Universe; BIONICLE Legends 6: City of the Lost)
Two natural traits distinguished the Hydruka from most other PitThe PitThe Order of Mata Nui's maximum-security underwater prison where the Barraki warlords were held until catastrophe broke their chains. fauna. The species could fire Solidified Air Bubbles from natural launchers at the ends of their tails, and the air inside was toxic to water-breathing creatures. Hydruka could also tell strands of AirweedAirweedThe underwater plant of the Fields of Air whose bubbles let the Matoran of Mahri Nui breathe beneath the sea. holding usable air from those that did not, and they were tireless workers able to carry heavy loads. (BIONICLE: Encyclopedia Updated)
That mix of selectiveness and stamina made them ideal working animals for the Mahri NuiMahri NuiA matoran settlement that sank, survived, and was ultimately crushed beneath Voya Nui, leaving behind one of Bionicle's most poignant lost civilizations. MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body., who named many of them to keep track of their herds. Two named individuals are recorded: MorakMorakMorak was a Hydruka of Mahri Nui, one of two named members of the air-harvesting species that kept the underwater Matoran colony alive., a stubborn but skilled blue Hydruka with a glowing carapace, and ThuloxThuloxThulox was a Hydruka assigned to the Fields of Air beneath Mahri Nui, harvesting airweed and wielding an Air Launcher for defense.. (BIONICLE Legends 6: City of the Lost; BIONICLE: Encyclopedia Updated)
The Airweed harvest#
AirweedAirweedThe underwater plant of the Fields of Air whose bubbles let the Matoran of Mahri Nui breathe beneath the sea. was a plant native to the Fields of AirThe Fields of AirThe airweed beds on the seabed beside the sunken village of Mahri Nui, harvested by Hydruka under Matoran supervision to supply the air bubbles that kept the settlement alive., characterised by trapped pockets of breathable air within its structure. When Mahri NuiMahri NuiA matoran settlement that sank, survived, and was ultimately crushed beneath Voya Nui, leaving behind one of Bionicle's most poignant lost civilizations. broke loose from Voya NuiVoya NuiAn island born from catastrophe and hiding the universe's most powerful artifact, Voya Nui was everything Bionicle 2006 promised: danger, mystery, and a race against time. and tumbled into the ocean, it collided with the Fields of Air, and the impact dislodged enough air from the AirweedAirweedThe underwater plant of the Fields of Air whose bubbles let the Matoran of Mahri Nui breathe beneath the sea. to form the bubble around the settlement, allowing the MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body. population to survive on the seafloor. (BIONICLE Legends 6: City of the Lost; BIONICLE: World)
Sustaining the bubble required continuous harvest. Over the following three centuries, the MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body. of Mahri NuiMahri NuiA matoran settlement that sank, survived, and was ultimately crushed beneath Voya Nui, leaving behind one of Bionicle's most poignant lost civilizations. tamed and trained Hydruka for the work, relying on their ability to pick out AirweedAirweedThe underwater plant of the Fields of Air whose bubbles let the Matoran of Mahri Nui breathe beneath the sea. that still held air. The job mattered enough that the post of Hydruka guard came into being. The animals could not be rushed: hurrying a harvest frightened or angered them, so they had to work at their own pace. (BIONICLE Legends 6: City of the Lost; BIONICLE: World)
The Hydruka were maintained in controlled enclosures known as the hydruka Pens, situated near the Fields of Air. BIONICLEBIONICLE: Matoran AdventuresA 2002 GBA platformer where you play as one of six Matoran fighting Bohrok across Mata Nui's islands. Legends 6: City of the LostCity of the LostThe first appearance of Mahri Nui in the Quest for the Mask of Life, the airweed harvest that kept the underwater city alive, Defilak's submarine expedition into the Black Water, and the arrival of the Barraki on the doorstep of the Matoran settlement. records KyrehxKyrehxKyrehx is a blue Ga-Matoran of the water element, though that power remains inaccessible to her. She serves as a Hydruka Guard and carries claws and blades. She resides on Spherus Magna. being attacked by animated air weeds at the Fields of Air close to these pens, while carrying a mask she had found, which turned out to be the Ignika. The Pens served as the base for the harvest. (BIONICLE Legends 6: City of the Lost)
Air Launchers#
The Air LauncherAir LauncherThe Air Launcher is a defense weapon used by the Matoran of Mahri Nui that shoots air bubbles. The device is no longer in use. was a ranged weapon constructed by the MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body. of Mahri NuiMahri NuiA matoran settlement that sank, survived, and was ultimately crushed beneath Voya Nui, leaving behind one of Bionicle's most poignant lost civilizations., modelled on the natural Solidified Air BubbleAir BubbleVital underwater survival items that kept Mahri Nui Matoran alive in the ocean depths. weaponry of the Hydruka. The weapon fired the same kind of projectile and relied on the same fact: the air was toxic to water-breathing creatures. (BIONICLE Legends 6: City of the Lost; BIONICLE: World)
The first artificial launcher was the work of a Le-MatoranLe-MatoranGreen-powered Matoran obsessed with thrills and transport. They're basically Bionicle's daredevils. scientist of Mahri NuiMahri NuiA matoran settlement that sank, survived, and was ultimately crushed beneath Voya Nui, leaving behind one of Bionicle's most poignant lost civilizations., who meant it as transport, with MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body. riding inside the air spheres instead of swimming. The idea died with its first test, when the scientist launched himself into the arms of a TarakavaTarakavaHuge lizard-like Rahi with powerful forelegs, hunted in pairs across Mata Nui and Metru Nui.. The design was thereafter repurposed as a shoulder-mounted offensive weapon. (BIONICLE Legends 6: City of the Lost; BIONICLE: World)
Air launchers were used by the Hydruka themselves, MorakMorakMorak was a Hydruka of Mahri Nui, one of two named members of the air-harvesting species that kept the underwater Matoran colony alive. and ThuloxThuloxThulox was a Hydruka assigned to the Fields of Air beneath Mahri Nui, harvesting airweed and wielding an Air Launcher for defense. among them, and by the MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body. defenders of Mahri NuiMahri NuiA matoran settlement that sank, survived, and was ultimately crushed beneath Voya Nui, leaving behind one of Bionicle's most poignant lost civilizations.. Following the MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body. evacuation back to Voya NuiVoya NuiAn island born from catastrophe and hiding the universe's most powerful artifact, Voya Nui was everything Bionicle 2006 promised: danger, mystery, and a race against time., the Air LauncherAir LauncherThe Air Launcher is a defense weapon used by the Matoran of Mahri Nui that shoots air bubbles. The device is no longer in use. passed out of active use. (BIONICLE Legends 6: City of the Lost; BIONICLE Legends 7: Prisoners of the Pit)
Predation and the Pit ecosystem#
The herds lived in dangerous waters. Mahri Nui sat beside the territory of the BarrakiThe BarrakiSix warlords who built an empire spanning most of the Matoran Universe, fell to a Brotherhood strike, and spent millennia imprisoned in the Pit., the warlords who had escaped the PitThe PitThe Order of Mata Nui's maximum-security underwater prison where the Barraki warlords were held until catastrophe broke their chains., and their sea creatures and armies were a constant threat to anything working the Fields of Air. (BIONICLE Legends 6: City of the Lost)
BIONICLEBIONICLE: Matoran AdventuresA 2002 GBA platformer where you play as one of six Matoran fighting Bohrok across Mata Nui's islands. Legends 7: Prisoners of the Pit confirms the operational cost of this predation. Following a Toa MahriToa Inika and Toa MahriSix ordinary Matoran transformed by lightning from the Red Star into heroes who ultimately revived the Great Spirit itself. operation in Mahri NuiMahri NuiA matoran settlement that sank, survived, and was ultimately crushed beneath Voya Nui, leaving behind one of Bionicle's most poignant lost civilizations., DefilakDefilakDefilak is a dark green and silver Le-Matoran who serves as leader of the Mahri Nui Council and as an inventor. He wears a powerless Kualsi and wields Electro-Blades alongside an Air Launcher. As a Le-Matoran, he carries an inactive affinity for the element of Air and resides on Spherus Magna. was recorded as distressed at the deaths of several Hydruka and MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body., and at the consequent loss of the safe hour the city's residents had depended on for harvest. His reaction shows how much the city valued its herd. (BIONICLE Legends 7: Prisoners of the Pit)
Aftermath of Mahri Nui#
The destruction of Mahri NuiMahri NuiA matoran settlement that sank, survived, and was ultimately crushed beneath Voya Nui, leaving behind one of Bionicle's most poignant lost civilizations. and the subsequent return of its MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body. population to Voya NuiVoya NuiAn island born from catastrophe and hiding the universe's most powerful artifact, Voya Nui was everything Bionicle 2006 promised: danger, mystery, and a race against time. ended the working relationship between Hydruka and the MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body.. The surviving Hydruka population remained in the sea. The species did not follow the MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body. back to the surface, was not absorbed into Toa MahriToa Inika and Toa MahriSix ordinary Matoran transformed by lightning from the Red Star into heroes who ultimately revived the Great Spirit itself. operations, and is not recorded further in surviving accounts of the Matoran UniverseMatoran UniverseA civilization of biomechanical beings living inside a colossal robot, destroyed when Teridax seized control.'s remaining period. (BIONICLE Legends 8: Downfall)
The end of the relationship came from changed conditions rather than abandonment. The Hydruka's value to the Mahri NuiMahri NuiA matoran settlement that sank, survived, and was ultimately crushed beneath Voya Nui, leaving behind one of Bionicle's most poignant lost civilizations. MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body. had rested on their ability to harvest AirweedAirweedThe underwater plant of the Fields of Air whose bubbles let the Matoran of Mahri Nui breathe beneath the sea., and once the city was gone there was no air bubble to keep alive. (BIONICLE Legends 8: Downfall)
Significance#
The Hydruka was a load-bearing species in the Mahri NuiMahri NuiA matoran settlement that sank, survived, and was ultimately crushed beneath Voya Nui, leaving behind one of Bionicle's most poignant lost civilizations. period, responsible for the harvesting work that maintained the settlement's air bubble and the natural prototype for the principal ranged weapon used by its MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body. population against the BarrakiThe BarrakiSix warlords who built an empire spanning most of the Matoran Universe, fell to a Brotherhood strike, and spent millennia imprisoned in the Pit. and their forces. Their knack for finding air-filled Airweed was the basis of that whole relationship. (BIONICLE Legends 6: City of the Lost; BIONICLE: World)
Following the destruction of Mahri NuiMahri NuiA matoran settlement that sank, survived, and was ultimately crushed beneath Voya Nui, leaving behind one of Bionicle's most poignant lost civilizations., the colony stayed in the sea and passed out of MatoranMatoranThe most abundant species in the Matoran Universe, chosen by Mata Nui to inhabit and maintain his cosmic body. management. (BIONICLE Legends 8: Downfall)
Frequently asked questions
- What is a Hydruka?
- The Hydruka was an aquatic scorpion-like Rahi species native to the Pit, created by the Makuta from viruses and liquid protodermis. The Matoran of Mahri Nui later domesticated the species to harvest Airweed.
- What were the Hydruka used for in Mahri Nui?
- The Matoran of Mahri Nui domesticated Hydruka as herd Rahi to harvest Airweed, exploiting the species' natural ability to distinguish Airweed from ordinary seaweed in the Fields of Air. The harvested Airweed sustained the air bubble that kept the settlement alive on the seafloor.
- What natural abilities did the Hydruka have?
- The Hydruka could generate and launch Solidified Air Bubbles, projectiles of compressed air that were especially dangerous to water-breathing species when the bubble dispersed on impact. They were tireless, could carry heavy loads, and could also defend themselves with their teeth.
- How is the Hydruka connected to the Air Launcher weapon?
- The Air Launcher was a ranged weapon built by the Matoran of Mahri Nui, modelled on the natural Solidified Air Bubble weaponry of the Hydruka. It fired Matoran-scale versions of the same projectile and was used against water-breathing targets.
- What happened to the Hydruka after Mahri Nui was destroyed?
- The destruction of Mahri Nui and the return of its Matoran population to Voya Nui ended the working relationship, and the surviving Hydruka population remained in the sea. The species did not follow the Matoran to the surface and reverted to wild Pit fauna.
Gallery

Images via BIONICLE Wiki (Biosector01)
Sources
- BookBIONICLE Legends 6: City of the Lost, Greg Farshtey, Scholastic, 2007
- BookBIONICLE Legends 7: Prisoners of the Pit, Greg Farshtey, Scholastic, 2007
- BookBIONICLE Legends 8: Downfall, Greg Farshtey, Scholastic, 2007
- BookBIONICLE: Encyclopedia Updated, Greg Farshtey, Scholastic, 2007
- BookBIONICLE: World, Greg Farshtey, Scholastic
- BookBIONICLE: Makuta's Guide to the Universe, Greg Farshtey, Scholastic, 2009
Spotted a factual error or a primary source we missed? Email a correction. Every flagged claim gets reviewed.
Followed from this entry

Morak
Morak was a Hydruka of Mahri Nui, one of two named members of the air-harvesting species that kept the underwater Matoran colony alive.

Thulox
Thulox was a Hydruka assigned to the Fields of Air beneath Mahri Nui, harvesting airweed and wielding an Air Launcher for defense.

Airweed
The underwater plant of the Fields of Air whose bubbles let the Matoran of Mahri Nui breathe beneath the sea.

The Fields of Air
The airweed beds on the seabed beside the sunken village of Mahri Nui, harvested by Hydruka under Matoran supervision to supply the air bubbles that kept the settlement alive.

The Pit
The Order of Mata Nui's maximum-security underwater prison where the Barraki warlords were held until catastrophe broke their chains.
Air Bubble
Vital underwater survival items that kept Mahri Nui Matoran alive in the ocean depths.
Mentioned in14 entries
Airweed
The underwater plant of the Fields of Air whose bubbles let the Matoran of Mahri Nui breathe beneath the sea.
City of the Lost
The first appearance of Mahri Nui in the Quest for the Mask of Life, the airweed harvest that kept the underwater city alive, Defilak's submarine expedition into the Black Water, and the arrival of the Barraki on the doorstep of the Matoran settlement.
Engineer
Engineers, also called Inventors, were Matoran whose work was to build the machinery and devices that improved life across the Matoran Universe, a trade most famously held by Nuparu, builder of the Vahki and the Boxor.
Morak
Morak was a Hydruka of Mahri Nui, one of two named members of the air-harvesting species that kept the underwater Matoran colony alive.
Mutagen
Pit Mutagen was a power-source energy that leaked into the waters of The Pit during the Great Cataclysm and mutated almost every being exposed to it.
Reysa
Reysa was an impatient Onu-Matoran Hydruka shepherd of Mahri Nui whose unexplained death at the Fields of Air opened the chain of events that put Defilak's submarine into the Black Water and exposed the Barraki to the underwater city.
The Fields of Air
The seabed meadow of airweed whose bubbles kept the sunken village of Mahri Nui breathing inside fragile pockets of borrowed air.
The Fields of Air
The airweed beds on the seabed beside the sunken village of Mahri Nui, harvested by Hydruka under Matoran supervision to supply the air bubbles that kept the settlement alive.
The Matoran Council
The governing body of the sunken city of Mahri Nui, a rotating council of Matoran leaders who met monthly in the Council Chamber of the Mahri Nui Fortress to plan the city's future, distribute the gifts from above, and decide the response to the Barraki incursion.
The Toa Mahri Descent into the Pit
The transformation that ended the Toa Inika, the Barraki's war on the newcomers, and the moment Matoro learned that his Maxilos escort was Teridax.
Thulox
Thulox was a Hydruka assigned to the Fields of Air beneath Mahri Nui, harvesting airweed and wielding an Air Launcher for defense.
Air Bubble
Vital underwater survival items that kept Mahri Nui Matoran alive in the ocean depths.
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