The Hidden Swarm are the first Hive encountered in The Dark Within. On the Moon, they're the outermost defensive line, warding off anyone attempting to enter the Hellmouth. They are identified by their red-orange coloring and the large nails driven through their arms and bodies. This sect of Hive is encountered once more on Luna in Shadowkeep; their general look remains the same compared to Savathûn's Hive but they now seem to have some form of spiked growth all over their bodies.
Arrival in the Solar System
When Crota, Son of Oryx and his spawn arrived at the Solar System and took over the Moon, The Hidden Swarm served as the beachhead force for Crota's staged invasion of Earth and also tasked with protecting their newly erected lunar strongholds, the most infamous of which being the Hellmouth. As they silently built their strength over the centuries, a Titan named Rezyl Azzir happened to intrude upon the Hellmouth and met with the Hive Wizard Xyor, the Blessed and her consort Knight. Though Rezyl survived his encounter, it would ultimately be Xyor's plan to curse the Titan with her dark whispers into becoming the infamous Dredgen Yor.
During the early City Age, the Hidden Swarm launched their Seeder Ships throughout Earth and engaged the Light-bearing Guardians at the Rusted Lands in the Eastern Flooded Zone; only one surviving Hunter warned the City of the Hive threat. Against overwhelming odds, the Guardians barely succeeded in repealing their forces at the Battle of Burning Lake, only to fail at their counteroffensive at the Great Disaster on the Moon.
Unopposed after their victory at Luna, the Hidden Swarm continued to seed their brood in secret beneath Old Russia for years, until Fallen from the House of Devils stirred them up at Skywatch much to the discovery of a newly-Risen Guardian. With word reaching the Speaker about the resurgence of Hive activity on Earth, the Guardian was sent to investigate the Hellmouth for answers. What they found confirmed that the Hive was preparing a second invasion of Earth; this time also attacking the dormant Traveler in a ritual to drain its Light using a lost shard of it. The ritual was thwarted but the threat of the Hive remained; one which would be addressed by the former-Lightbearer Eris Morn.
Having sworn vengeance on the Hive and their master Crota for the losses of her Light, Ghost, and fireteam, Eris took tactical control over the Guardian operations as they work to dismantle the leadership behind the Hidden Swarm, including the legendary Swarm Princes (whom forged Crota's infamous Sword) and their commander Sardon, Fist of Crota (whom lead the Hive spawn on Earth). Eventually, Crota fell to the Guardians, though word of his death would reach his father: Oryx, the Taken King.
Years after Crota's death and that of Oryx, the Hive on Luna would remain relatively quiet. As the attention of the Guardians became preoccupied with the chaos of the Red War, the conflicts on Mercury, Mars, and in the Reef, the Hive on Luna would be overlooked. As a result of numerous deaths, the various broods on the Moon consolidated into the Hidden Swarm, becoming the "de facto" Hive power on the moon. Rallying under the banner of the scheming Daughters of Crota, led by Hashladûn, the Hidden Swarm sought power to turn their situation around, constructing a massive crimson fortress, the Scarlet Keep, that would act as an amplifier for their magics and to defend the Pyramid.
Hashladûn and her coven of sisters sought to use the Pyramid's power and connection to the Darkness to provide them the means to turn their situation to their advantage and exact vengeance against the Guardians for ravaging their lineage. Using a forbidden piece of arcane knowledge, the Cryptoglyph, Hashladûn and her sisters experimented on the phantasmal essences created by the Pyramid in a fruitless attempt to recreate the essence of their deceased King, Oryx. However the Hidden Swarm was soon marred by corruption and conspiracy from within, as Hive distrusting of the Daughters' leadership enact a conspiracy to usurp them in defiance of Oryx's Sword-Logic. Their conspiracy failed as it caught the attention of Savathûn, the Witch-Queen, furthering her greater schemes in exchange of aiding her grand-nieces in giving them necessary tools to challenge the Risen. Eventually, the discovery of the Pyramid beneath Luna's surface by Eris Morn provided such an opportunity, creating phantasmal Nightmares based on the Guardians' traumas that the Swarm could exploit in the battle to come.
The Guardian would soon enter the Scarlet Keep to investigate but would soon discover the Pyramid and encounter the Nightmares for the first time, nearly getting overwhelmed as the Nightmares took the form of Crota, Dominus Ghaul and Fikrul, the Fanatic. Fortunately, Eris Morn would rescue the Guardian and soon lead the charge against the Hidden Swarm. Gaining the Vanguard's support, Eris Morn guided the Guardians into dismantling the Hidden Swarm's power base while seeking a way to enter the Pyramid. The Guardians would soon enough confront Hashladûn herself within the Scarlet Keep, managing to slay the eldest of Crota's daughters at the peak of the Tower of Woe. Further, the Guardians braved the darkness of the Hive's most forbidden sanctum, the Catacombs, to acquire the Cryptoglyph so Eris could create armor to combat the Nightmares, slaying Besurith, Daughter of Crota in the process. Such actions were critical blows to the Hidden Swarm but they would remain a threat the Guardians continue to fight against as well as containing the Nightmares.
Return of Zulmak
Currently, the last of Crota's spawn, Voshyr and Kinox, remain in hiding, seeking power regardless of the means going against the Sword-Logic to ensure that the legacy of their father and grandfather does not fade. The remaining daughters of Crota made use of a weapon they gained following the failed conspiracy within the Pit beneath the Scarlet Keep: a reanimate Knight that became their puppet champion named Zulmak, Instrument of Torment. Using demented rituals that involved sacrificing Nightmares to an Ascendant Crystal to empower Zulmak, the daughter of Crota aimed to use their puppet to stand against the Guardians. However, as their Altars of Sorrow rituals caused seismic disturbances, the Guardians were alerted to their activities.
Delving deep beneath the Keep, the Guardians explored the Pit of Heresy and encountered powerful Hive, Disciples of the Broken Blade. After slaying each disciple and solving intricate puzzles, the Guardians managed to reach Zulmak's lair, the Cradle of Damnation. There, the Guardians faced off with the Daughters' puppet but despite his strength and his Ascendant Crystal, the Guardians used his own Swords and magic against him, bringing the monster down. However, due to the Daughter's forbidden use of necromantic sorcery, Zulmak continually revives after every slaying, forcing the Guardians to return to the Pit and kill Zulmak.
List of appearances