In 814.M41 a barely coherent message from a patrol group above Herisor that claimed that the Tyranids had arrived reached the Achilus Crusade command.
An uncommonly large Deathwatch taskforce was assembled, fighting to cleanse the planet of the Tyranid menace yet reporting devastating initial losses due in large part to attacks from Harridans and associated Gargoyles.
While the smaller xenos flyers distracted ground troops with swooping attacks and strafing runs, the Harridans crippled Imperial aircraft, thereby preventing effective air transport of ground troops.
It is well known throughout the crusade's Orpheus Salient that less than half of the Space Marines who fought on Herisor survived. Many of those who fell in these battles lost their lives to Tyranid Harridans.
In the final years of the 41st Millennium, it was reported by Battle-Brother Aelianus that a Genestealer horde was threatening to overrun a Deathwatch-held position on the southern landmass of Herisor.
The drop went off without difficulty. As they entered the atmosphere, the squad prepped for disembarking. At 3500 metres to target, their paired Thunderhawk, the Acanthus, experienced a mid-air collision with a flying xenos, which Brother Martinus identified as a Harridan. The Acanthus plummeted to the ground and exploded.
The Kill-team later confirmed that none aboard survived.
Aelianus' Thunderhawk, the Eligius, began to veer and jink rapidly. He assumed their pilot was engaging in evasive manoeuvres. Soon after, he heard the ship's Heavy Bolters open fire, and through the gun port periscope, he could see at least two Harridans flying nearby.
At about 1000 metres to the target, his pilot pulled up suddenly. Aelianus felt an impact, and the Eligius went into a spinning dive. He saw the other Rhino tear free from the Thunderhawk's grapple arms and fly away. Moments later, they hit the ground sideways, crashing and sliding for a few hundred metres.
Only three of Aelianus' ten-man squad survived the crash, including himself, Brother Lucianus, and Brother Marinus, who was badly injured in the crash. They spent several solar minutes extricating themselves from the wreckage.
They emerged to find themselves about 1.5 kilometres from their drop target. About 150 metres from the wreckage lay the injured body of the Harridan that must have hit them. It was writhing in its death throes, its left wing and shoulder a devastated ruin.
Aelianus' team had just enough time to confirm that the pilots of the Eligius were dead before the Genestealers attacked. They took cover in the wreckage and thereby managed to hold off the Genestealers for several solar minutes with sustained bolter fire. The Genestealers attacked relentlessly, and Lucianus fell.
Marinus shot the Genestealer who killed Lucianus but was in turn slain by yet another Genestealer. Falling back further into the wreckage, Aelianus was able to gun down the remaining three Genestealers.
- Deathwatch: The Jericho Reach (RPG), pp. 112-113, 156, 157, 171, 177-178