The Pretty Marines are one of /tg/'s homebrewed Space Marine chapters, created by taking the stereotypical bishounen warrior, who is mysteriously incredibly beautiful despite following a career path that requires him to engage in deadly and typically disfiguring combat on a frequent basis, and transplanting the idea into the Warhammer 40,000 setting.
They were the Second Space Marine Legion, and once their Primarch; the ironically named Augrim Gorfist (look, the people of the planet Cerulea thought it would be funny) was reunited with them, they set to work on prettifying space though they were generally ignored by all the other legions save for Horus and the Luna Wolves (because Horus was nice to all his brothers till he you know...did some epic heresy), Sanguinus and the Blood Angels (as fellow bishonen the Blood Angels felt kinship for the impossibly youthful looking Pretty Marines...although it might have just been pity, considering that the Blood Angels actually managed to Get Shit Done), and Fulgrim and the Emperor's Children (Again, Bishonens stick together.)
When the Horus Heresy came the Pretty marines split in two, one wishing to fight for Slaanesh and stand by the Emperor's Children, the other staying loyal to the Emperor and stood by the Blood Angels. Horus then promptly beat the living shit out of the loyal half and prevented them from participating in the siege of Terra. Augrim Gorfist and many of the remaining loyal Pretty Marines disappeared into the Webway, following the example set by Jaghati Khan. As there were not enough Pretty Marines left for Roboute Guilliman to turn into a full chapter, Guilliman had them sit on Cerulea and rebuild, but after he was poisoned by Fulgrim's cheating ass poison blades, a bureaucratic mishap struck the 2nd legion from Imperial Records.
10,000 years later the pretty marines finally had enough marines to turn their former legion into a chapter and make a few successor chapters, but by the very next day they lost their entire 3rd, 4th, and 2nd company to Angron's Dominion of fire campaign when the World Eaters came to break Planet Cerulea's back, with the company commander being stomped into a red paste by Angron himself while the Librarian was slaughtered by Kharn. A few centuries later the Pretty Marines joined the Space Wolves in the first war of Armageddon and sent their entire chapter to redeem themselves. Angron, Kharn, and An'ggrath killed 60% of the chapter with another 39% falling to the other Khornates, leaving only the first Terminator Veteran squad of the first company, three tech-marines, two dreadnoughts, a land raider, and a Gladius frigate. They have only now finished the painstaking task of restoring their numbers to full.
Created by the Imperium as a symbol of human perfection and grace, all members of the Pretty Marines are selected for their dashing good looks, androgynous charm, and combat prowess. The Pretty Marines excel in covert warfare, sabotage, parades and flower arrangement. The chapter emblem is a rose on a field of white and the powered armor is commonly painted lavender augmented with various pastels. They are often depicted going into battle carrying microphones, as a parody of boy bands manufactured for teenage girls.
Unique to the Pretty Marine geneseed is a specialized organ called the "Sparkle Gland", the source of the Pretty Marine's powerful and mysterious sparkle attacks. A mutation of the Occulobe, it increases the functionality of the eyes and tear ducts. When a Marine sheds tears, the liquid will provide rapid healing of any wound it touches. Additionally the pupils can cause minor forms of hypnotic phenomena in subjects looking directly into the Marine's eyes. The phenomena commonly manifest as increased glamour of the Marine or hallucinations of "bubbles" or "sparkles".
The Pretty Marines also come in a Chaos version.
Sadly for the Pretty Marines, like all other Space Marines they are Sterile and lack testicles (indeed all glands that produce Testosterone and Estrogen are removed in the process of creating Space Marines) to prevent the most basic of urges from interfering in their duties, thus they can never truly please their legions of fangirls in the way that the fangirls, deep down, really want to be pleased. Many a Pretty Marine has had to shamefully reveal this fact to many a very disappointed and now disillusioned fangirl in the bedroom.
However, not all pretty marines are complete fags and useless idiots. A small group, disgusted that their Chapter was turning into a bunch of prideful, mirror and rose toting assholes, separated. led by Sergent Kamina and brother Rei, currently they are GETTING SHIT DONE.
 Tales from the Battlefield
Collected from the field reports of many industrious Anonymii.
Tales from the Battlefield: A data log of Imperial Battles by Adept Scribe Manfold the Note-Taker.
Chapter XXIV: The Rose's Thorns. The Battle of Gerlei II.
Privy to information from rogue traders of an Ork invasion upon the verdant world of Gerlei II, I arrived to find PDF forces already fighting a bloody and brutal trench war with the savage greenskins. May the Emperor bless those fine men for their valor in the face of such a horde (and forgive me for not fighting), but they were outnumbered.
All appeared to be lost at the main hive, when a strange procession made its way towards the battle. Resplendent in their purple armor and bearing the symbol of the rose upon their shoulders and banners, I beheld the Pretty Marines in their glory. As they advanced the air seemed to clear, the sun appearing to shine directly upon their battle-ready forms. Behind them was a procession much like one I had seen of pilgrims following Sororitas as they marched to war, though instead of flagellating zealots I saw a throng of screaming fourteen year old girls.
In war they were as any Astartes, brutal and swift. The Ork horde were caught in the sudden counter-attack spearheaded by assault troopers who glided gracefully overhead before diving upon greenskins like an eagle swooping upon its prey.
The Orks were annihilated utterly, but the marines did not celebrate. They left the battlefield, bearing the body of one of their own in a mournful procession. I managed to get a hold of one of their scouts to ask him what had occurred to fell this brave warrior, for no marks appeared to adorn his form.
"No marks?!" the scout had exclaimed at me, manly tears streaming down his face, "Those greenskins cut his cheek! His beautiful features are marred forever!"
The wailing of the little girls lasted well into the night and the next day.