Battle of Duriel
In the aftermath of the original battle with Kraken, Iyanden's Farseers had created a Warp Storm to block the Tyranid pursuit. Hundreds of Bio-ships had been caught in the tempest, and the Eldar had assumed them destroyed. However this was not the case, and thanks to the prophecies of Taec Silvereye, Iyanden learned that Kraken's remnants had been returned to the Materium. Worse still, it seemed that Kraken's remains was heading towards Hive Fleet Leviathan, and the Eldar knew that if the fleets were to combine the results could be catastrophic. The Eldar bio-information that Kraken had consumed could be merged with Leviathans resources, creating an unstoppable strain of Eldar-Tyranid hybrids. Thus the Eldar surmised to stop Kraken once more, this time at the world of Duriel. Iyanden was soon aided by Biel-Tan and surprisingly the Dark Eldar of Commorragh in their efforts. Harlequins were able to broker this alliance. The Dark Eldar provided the solution to defeating the Tyranids: triggering a psychic device called the Fireheart that would destroy the core of Duriel and all the alien beasts with it. However it could not be detonated remotely, so the Eldar knew that whoever stayed behind to activate the device would perish with Duriel.
Soon enough Duriel had erupted into conflict as the Swordwind of Biel-tan arrived first and bore the brunt of the initial fighting. However Craftworld Iyanden soon came under attack despite not having reached their destination. The unthinkable had happened: the Webway Nexus on Duriel had been compromised, sending swarms of Tyranids through it. Silvereye immediately ordered his Wraith-constructs to defend the Craftworld's own Webway gate and prevent Iyanden itself from being overrun. Soon enough Iyanden's Avatar was awoken and plunged itself into the Tyranid horde. With the aid of the mighty personification of Khaine, the Eldar were able to push the Tyranids back into Iyanden's Webway gate and onto the surface of Duriel itself.
Iyanden's forces arrived to discover the final battle at Duriel was already underway at a mountain known as Godspeak. Here Biel-tan's Farseers sought to activate the Fireheart as a force of Eldar and Dark Eldar fought to keep the Tyranids at bay. The Eldar fought to the last as the Fireheart was activated and Duriel began to implode. As the planet exploded, Yriel led Iyanden's fleet against the Tyranid Bio-ships in orbit alongside Dark Eldar Attack Craft and finished them off, denying the fusion of Kraken and Leviathan. The Eldar had emerged victorious, but at heavy cost. Worse still, Taec Silereye had perished in Duriel's destruction.