The Sacking of Gassan Prime

In late M40 Gassan Prime, location of the Fortress-Monastery of the Rift Flames chapter of Space Marines, was sacked by countless thousands of daemons and traitors alike lead by a dark council of Greater Daemons and Daemon Princes, ultimately resulting in the destruction of the entire planet and the annihilation of over 900 Rift Flame marines. It is still unknown who or what managed to unite such a great horde of the servants of Chaos, and the reason for the invasion also remains a mystery.

Although the identity of almost all of the assailants and their warbands is unknown to all but a handful of individuals, the fraction that are known to Imperial records are listed below

Auriax the Opulent
Greater Daemon of Slaanesh, Auriax is reported to have lead the campaigns on Gassan's southern continents, plundering and hoarding the wealth as he went. His followers proclaim that ultimate power comes from obscene levels of material wealth, and rumours speak that whole planets are covered in his hoardes of riches.

Ghorak, Thy Flesh Consumed
Ghorak is said to have ascended to Daemonhood and have taken control of his warband (The Blooded Maw) by betraying his former Lord and eating him alive. Ghorak and his cannibalistic warriors let loose a terror campaign across the hives of Gassan, ravenously consuming their victims, human and Astartes alike (and occasionally each other). Ghorak himself is said to have executed the Captain of the Rift Flames Sixth Company by consuming him alive.

Hrahras the Hider
A Chaos Lord cursed with being perpetually ill equipped, Hrahras took the opportunity of The Sacking to raid and loot. His warband are a ragtag crew of thieves and rogues, all in poorly fitted armour that was stolen and (sometimes) hastily repainted. Trailing the destruction wraught by other, more efficient warmasters of Chaos, Hrahras followed behind like a vulture to plunder anything useful from the ruins.

Per'suel
A vile and cunning Daemon Prince, such is Per'suel's zeal that he attracts followers of Khorne and Tzeentch alike. Immensly sadistic, Per'suel and his warband were responsible for the prolonged torture and subsequent massacre of the entire Eight Comapny of the Rift Flames. A millenium later the chapter managed to hunt down Per'suel and, with the assistance of the Feles Iratus, executed Per'suel and his followers on the desolate world of Umbra. It was Venerable Ancient Beowulf, interred in his Dreadnought sarcophagus following near fatal injuries during The Sacking, who annihilated the Prince.

Skabyris the Contagious
Great Unclean One Skabyris lead his Plaguebearers and Plague Marines in spreading vile miasmas and feculent diseases all across northern Gassan. Jolly and gregarious, Skabyris was filled with glee as his plague claimed many lives, more and more succumbing and joining him as his children. Midway through The Sacking, an orbital strike from an Astartes cruiser reportedly destroyed Skabyris, but hours later, unexplainably, he was seen unscathed thousands of miles away from the impact site.

Syrugaru the Pleasant Rose Air
A egomaniacal Daemon Prince of Slaanesh, Syrugaru spouts endless reams of poetry and rhetoric. Only referring to himself in the third person, his chosen followers aid him in creating beautiful and haunting works of art, usually in the form of careful mutilation. With the assistance of his hordes of Daemonettes, he splayed over six thousand civilians to form a sculpture of himself that could be seen for miles away. Although a relatively small warband, Syrugaru's Chosen were a lethal force during The Sacking, slaughtering battalions of guard and cities of civilians in the name of Syrugaru's perverse and twisted art.

Xyphylylius the Consort
A completely incomprehensible Greater Daemon of Tzeentch, many of Xyphylylius' enemies crumple with insanity upon seeing his ever-changing form. His Consortium of Lesser Daemons, cultists and traitor Astartes infiltrated countless hab-centres and bases on Gassan, some even making it into the Fortress-Monastery itself. Reports of Chaos forces "melting into pools of living water" may have arisen from the Consortium's sorcery. Once hidden in plain sight, Xyphylylius' servants opened up great portals, opening the way for screaming eldritch monstrosities to break loose from The Warp into reality, gibbering and wailing as they went. The Consortium gradually disappeared from Gassan about halfway through the campaign, never to be heard of from within the sector ever again, the reason known only by the eternally confounding Xyphylylius.