Sanguinary Guard
The Sanguinary Guard are a elite squad of Marines that are available only to the Blood Angels and their successors. The Honour Guard of a Blood Angel Commander on the battlefield, these Marines are as deadly as they look fabulous, and they are very fabulous.
The story of these scrotum crushing badasses stretches way back to the times when Sanguinius reunited with the Emperor and assumed command of the IXth Space Marine Legion.
At first they started as their Primarch's bodyguards, always following him through the worst (they even took part in the boarding of Horus's flagship). After Sanguinius's death at the hands of Horus, the only surviving member of this inner order was Azkaellon (simply because Sanguinius insisted that he stayed on Terra during the Siege).
Azkaellon was sad that he couldn't participate in the battles alongside his Primarch, yet he knew that he couldn't jeopardize the final orders he was given. When the Horus Heresy finally ended and Raldoron became the first Chapter Master, Azkaellon made sure that apart of the Blood Angels, every single of their successors would have their own Sanguinary Guard, so that these warriors wouldn't die out. The other purpose (and even truer than simply maintaining them) was to maintain them as a symbol of hope for the Imperium, as well as a living legacy for the space angel vampires.
To become one is not simply a field duty or honour of the highest calibre. To be a Sanguinary Guard is to become part of a order of those that can be described as mortals-become-gods, as well part of a living legend that is over ten thousand years old.
On the fields of battle, these warriors act, as mentioned before, Honour Guards of a Force Commander. Armoured in the best Artificer Armours, as well having Death Masks and Winged Jump Packs, the Sanguinary Guards are a impressive sight to behold. Their standard weapons are the Glaives Encarmine (that take the forms of axes and swords) and the Angelus Bolters (which are both more powerful than standard Bolters, and are mounted on their armours wrists, leaving the Guard with a free hand to wield their Glaives), causing them to unleash immense amount of Cleave and Smite up close.
The Sanguinary Guard's looks differ marginally among the Blood Angel's successors (with only the right pauldron being painted in the successor's symbol and colours). The only exception are the Angels Encarmine, who paint their Sanguinary Guard's armours in alabaster white and black wings, as opposed to the traditional gold with white wings (though even the wing colours differ from successor to successor).