Eldar reclaim Saim Lann

The Eldar still had unfinished business in the Shadow Worlds in 02.011M42. The colony of Saim Lann was still infested by the tyranid menace of hive fleet Nemesis, though the hive fleet itself had seemingly long since moved on. Even their attacks on Betor had become more sporadic and the war there had entered a dormant phase.
Even so the Eldar lacked the resources to defeat even the small infestation of their exodite colony, and with the Tyranids still there they couldn't complete their ultimate goal, re-hiding their Shadow Worlds colonies, cloaking them once again from the threat of outsiders.

One farseer however knew how this could be achieved. The world of Saim Lann harboured an ancient eldar defence mechanism, though the workings of it were incomplete and the Tyranids swarmed around the sacred ground where the warlocks of the eldar would be able to reactivate it. For weeks the eldar had been raiding their old territories searching for clues as to where the ancient artefacts necessary to fix the defence mechanism were situated. Now they knew.

The Eldar fell upon the Imperial colony of Aganthus, one of their ancestral homes, and attacked the Space Wolf force there taking them completely by surprise. The Imperial superhuman warriors put up strong resistence after their initial shock, but the raid bought the eldar enough time to retrieve an ancient artefact from a series of ruins close to the main Imperial base.

Now the eldar had the means to defeat the Tyranids and moved against them in as much force as they could muster. The battle around the ancient defence control station raged for several hours as the hive mind of Nemesis realised the intent of the eldar and the significance of the three control stations for which they were fighting to control.

Nemesis mustered as much force as they could against the eldar, but the swiftness of the children of Asuryan was too much for the tyranids to counter. At the climax of the battle a mighty Tervigon clashed with the incarnation of the bloody handed god himself, but the divinity of avatar of Khaine would not be stopped. Nemesis threw more creatures at the living god but it destroyed them all.

With the tyranid horde occupied with the titanic struggle against the avatar the rest of the eldar army captured one of the main control sites governing the eldar defence mechanism and with a horrific scream which echoed around the planet every alien beast dropped dead instantly, leaving Saim Lann in the caring hands of the eldar once more.