Shadow of the Great Devourer

The Shadow of the Great Devourer was a xenocidal purgation campaign conducted against an encroaching bioship of the ravenous xenos, known as the Tyranids, that invaded the home system of the Blood Serpents Space Marine Chapter sometime in M36.

History
Five days after Kuthru Zarlan's forces had been defeated a strange living ship appeared above Astoran, and immediately attacked, and destroyed what remained of the defensive fleet above Astoran. The weird living vessel then immediately launched several spores down to the planet. The hoards of strange creatures immediately ran forwards, and found the tunnel network, pouring down and overrunning the first few marines that they came across. The beasts slowly fought their way through Astoran before the Blood Serpents mount a combined assault pushing the creatures back to the surface.

Upon reaching the surface the remaining fifty Blood Serpents noticed that the ship had stopped dropping down reinforcements. However, there was one enemy force remaining, it appeared to contain: One giant monstrous leader beast, along with two groups of smaller leader beasts, along with a massive swarm of lesser creatures. The Blood Serpents devised a plan, have the two remaining Captains each take fifteen marines to attack the flanks, and remove the smaller leader beasts, before having the entire army launch an assault on the central larger leader beast.

The plan started off to a successful but rocky start, the two side teams managed to remove the smaller leader beasts, but at the cost of all but the two captains on the flanks. Additionally, the core army in the middle was taking heavy casualties. But all was not lost, for the central force pushed its way forwards, and Chapter Master Cronagg dueled with the monstrosity blocking the Blows from its mighty Sword, but then the creature lashed out with its whip and cut him down while he was blocking the sword, simultaneously the creatures two massive guns launched a barrage killing eight marines in one burst.

Then the two Captains converged on the leader alone, but they stood no chance as the creature sliced one in half while gripping the other with his whip, strangling him before throwing the unfortunate sole aside and blasting all but three of the remaining marines. Then Sergeant Skyrog stood up to the beast which prepared to swing its massive sword before its head exploded, and the beast fell over backwards crushing several smaller creatures.

The loss of the leader resulted in the rest of the creatures ran away, the remaining Blood Serpents then went on a purge of the remaining creatures. Then in space, the Apothicron arrived, and seeing the unknown ship, and no other Blood Serpent vessels immediately opened fire, bringing down the wounded ship.