The Coven of Isha is a secret pact between some members of the Ordo Xenos and the ancient Farseer Eldrad Ulthran of Craftworld Ulthwé. According to the Coven's librarium, the information provided by the Eldar through this pact has been linked to a number of disastrous events that engulfed the Imperium of Man, including the Sanapan Scouring, the Mortis Annihilation, the Third Coming of Orian and the First War for Armageddon. The Coven has rarely been invoked, for the Eldar rarely require the help of the Imperium, and the Imperium never looks toward xenos for help. The most recent time that the Coven was activated was when Deathwatch Space Marines from the Ordo Xenos had to help the Craftworld Ulthwé to counter the Dark Eldar's recent raids that took many Ulthwé prisoner to Hesperax, the homeworld of Lelith the Wych Queen. The prisoners were taken to be slain in Hesperax's gladiatrix games.
The great Eldar Farseer Eldrad Ulthran had created a special Wraithbone chamber hidden aboard the Inquisition's secret space station located in the Ramugan Sub-sector for the Ordo Xenos, which could be used for communication between the Inquistion and the Seer Council of Ulthwé. The Inquisitor Lord Seishon was summoned there to hear the request of Ulthran that the Imperium aid the Eldar in securing Craftworld Ulthwe by recovering a lost Eldar relic. The Inquisition's Ramugan space station had stood for millennia, and dated back to the time of the Great Crusade, when the Emperor Himself was still actively leading the Imperium. The station was home to delegations from the three main branches of the Inquisition: the Ordo Xenos, the Ordo Hereticus and the Ordo Maulleus.
The Seer Council of Ulthwe was convinced to accept aid from the "Mon-keigh", an action that some members of the Council, such as Ruhklo, saw as an insult. However, the Emerald Seer Thae'azki and the Seer Eldressyn - who had been chosen to serve on the Council by Ulthran himself - insisted on accepting the humans' aid. At last the decision was made. A Deathwatch Kill-team departed from Ramugan on the Lance of Darkness frigate by order of the Ordo Xenos to recover the relic for the Eldar and uphold the Coven of Isha. The Kill-team included the excellent Astartes from a wide range of chapters: Emperor's Champion captain Octavius originally came from the Imperial Fists, chaplain Luthar from the Revilers Vigilant, librarian Ashok from the Angels Sanguine, librarian Atreus of the Blood Ravens, Kruidan of the Mantis Warriors, the Iron Father Sulphus from the Red Talons and Pelias, Sergeant of the Black Consuls. They soon joined a conflict against a Dark Eldar's raid. Realising the Guardian of Ulthwe were somewhat weak, and the darkned soul of Ulthwe's citizen, the defenders barely had the courage to stand their ground and, even when support arrived, they retreated from the "mon-keigh". Next, they followed the request from warlock Shariele to patrol the Khalandhriel’s Hall of Ulthwe and confronted some Dark Eldar troops there. Abruptly, Ashok dissapered, although it would later be discovered that he was ordered by Lord Inquisitor Seishon to find the Infinity Circuit of Ulthwe and set up a beacon there so that the Inquisition can keep track of Ulthwe should it depart. He successed, but he was captured, disabled and taken to Hesperax by the Ulthwe's seers as a "gift", a secret bargain between the Emerald Seer Thae'azki and Lelith.
After wrecking havoc on the raid, the Deathwatch Kill-team was summoned to the seer council and was allowed to patrol the space and find traces of Dark Eldar movements. The Lance of Darkness departs, leaving the whole team and two Eldar: warlock Shariele and Shining Spears's Exarch Dhrykna behind. They soon find a squadron of Dark Eldar Corsair-class Escort, and give a chase. The Corsairs are no match for the Lance of Darkness, and only one of them escapes the assault, by order of Captain Octavius, so that they can find the Dark Eldar's base. The surviving Corsair flees for home via a warp gate that was camouflage as a asteroid. Soon after passing through the warp gate, Octavius finds Hesperax. He risks landing on the planet, wisely dividing his team into two Thunderhawks and sets off for the planet's surface. The first Thunderhawk was under command of Kruidan, and the second was commanded by Octavius. They dropped in to the planet atmosphere, where The Kruidan group landed first, and are ambushed by hundreds of Dark Eldars. Kruidan used his jet pack to repel the arriving enemy, bombing them from the sky. His squad fight fiercely, but are overwhelmed by waves after waves of darklings, so much so, that they are crushed and taken prisoner. Kruidan is shot down and wounded, his Power Amour broken at the back. Octavius's group didn't fare much better, as his Thunderhawk crash lands. Bythe time they are able to stand up, they are surrounded. They were "gifted" to the darkling by the treacherous Emerald Seer Thae'zaki, a secret bargain between her and Lelith the Wych Queen, to lure and trap some "mon-keigh" warriors in order to fight in the Hesperax's gladiatrix. This was predicted by Eldrad Ulthran long ago, and he directed this for his bigger achives.
The whole kill-team and two accompanied Eldar warriors were taken to the bridge. Their captors hadn’t even bothered to remove their power armour. Instead, the dark eldar had simply shackled the ankles and wrists of the Marines, pulling them tight against the wall. There was not a chain or a lock in the Imperium that could restrain a Space Marine in full combat armour, but these shackles were made of a material that they had never seen before — they appeared to be made out of the darkness itself. Kruidan was badly hurt and the darkling healed him to the point where he can stand and fight in the next round of the gladiatrix. Octavius was angered by the view of the remaining of human limbs and power armour remmants before him, evidence of the suffering inflicted on his brother Space Marine previously. No Deathwatch are taken here, though. Later, the two Eldar warriors are cut down and taken to the Gladiatrix to fight for entertaiment of thousand blood-thirsty Dark Eldars. With bare hands, they fought valiantly against three mounted Wyches. Shariele was able to kill one of the Wych and died, his soulstone ruined in combat. The Shinning Spear' sexarch Dhrykna still fight on. The whole Deathwatch kill-team are dragged here to see the show. The way they are shackled makes moving extremely difficult. Here they are reunited with librarian Ashok, who was put in a hardened cage. Shortly later, their body's locks are removed so that they could fight next.
In a room, Lelith meet the Slaanesh's Daemon Prince (who appered to be a immaculate princess with a breathtaking body). The Daemon princess seduced Lelith, the one who dared to toyed with Slaanesh's daemon, so that the Wych Queen could gather more souls to bring the princess (and her minions) into the materium realm. After a while, Lelith took her seat in the arena, with two other Eldarfarseers that were tasked with taking the temporarily disabled Ashok (though later Lelith informed them that they were sold goods, too). The old farseer Bhurolyn and the young Xhelkisor were shocked, and Bhurolyn slammed into the ground. But he immediately realised that Eldrad Ulthran would never betray him, and could it be himself was meant to be a last surprise for Lelith? The old farseer punched forward and sent a javelin of power crackling through the arena. It slammed into the massive, slowly opening doors and blew them apart, shattering them instantly, sending shards of metal and masonry flying around the amphitheatre like hail caught in a hurricane.The crowd went wild.
Dhrykna dashed over to aid the two farseers. The Deathwatch crushed the distracted darkling guards, each of them now wielded two darkling's swords. They fought back to back against wave after waves of gladiatrix's Wych. The crowd continued to go wild, shrieking and braying like wild animals: they had not seen such brutal yet exciting game recently. Suddenly a Talos Pain Engines enters the arena. Octavius was forced to deal with the new threat. The wych queen herself, who overcame by the voyeuristic thrill of combat, had vaulted down into the arena to join in. Both of Deathwatch librarian helps Dhrykna to deal with the Wych queen. Kruidan was already charging across the arena to assist his captain; Pelias and Luthar were giving chase to the fleeing wyches; and Sulphus was studying the mechanical monster that was attacking Octavius. Captain Octavius, with two ruined blades in his hands, was trapped by the Pain Engines. He struggles to detach himself from the barbed talons that impale him, but every movement simply drives the spines deeper into his flesh. When Kruidan arrives to help him, Octavius is nearly dead and almost consumed by the monstrous Engine. As he vanishes from view, Kruidan thought that he had heard the captain’s last defiant words, almost swamped in the cacophony of the arena: “Primarch — Progenitor, to your glory and the glory of Him of Earth!” Kruidan goes into a frenzy, climbing to hit it with his hardest blows. Sulphus, the Iron Father, also climbs up on top of the Engine and sets up a demolition charge inside it. The Engine spills shells anywhere, and with Sulphus last strike, the Engine explodes. Sulphus was able to get with him the yellow shoulder coat of the heroic captain. Dhrykna the Shining Spear falls to Lelith's poisoned blade, but is able to wound Lelith very badly. Lelith withdraws. Ashok helped to kill the suffered Dhrykna spirit stone instantly, and took her spiritstone - two other of the seers die with him so that their soul would be saved from the Dark Eldar
The remaining Deathwatch team dive out of the arena and into the shadowy corridor. Sulphus uses the explosives and shells taken from the wrecked Talos Pain Engine. demolishing a wall, thus blocking the chaser from catching them. They ran through a lobby that leads to a chamber, and here, Ashok confesses his knowledge about the plan. He informs them that this place was a nodal chamber, a place that hold the suffered souls of the Dark Eldars victims. It is also a navigation point that could lead to other places. When Sulphus sets up the explosives to demolish the place, The Wych finally surrounded them, and the Marines make a last stand. They fight valiantly to hold back the enemy. Then Sulphus activated the explosives and blows up the whole chamber.
The Marines flee to the gate with just enough time to get back to the Thunderhawk and then return to the Lance of Darkness. The freed souls of the long tortured release gigantic power surge, and the destroyed portal releases so much power from the Warp that Hesperax is totally incinerated. The plan to summon the daemon prince fails, but it is a close call.
The kill-team escaped the collasped world, and in return to Ramugan space station, they honoured their honourable and heroic captain that sacrificed his life for the mission.
- Warrior Coven (Novel) by C.S. Goto