Blood Angels
The Blood Angels were the 9th Space Marine legion created by the Empra and also known as the most batshit insane loyalist chapter in the Imperium without including the Angry Marines.
Their Primarch is named Sanguinius, a Marine who ironically has Angel like wings that mutated out of his back due to warp mutations in his homeworld Baal. Their current Chapter Master is a Marine named Dante, the oldest non-Dreadnought interred Space Marine in history.
They also had a brotherly rivalry against the World Eaters. Their chapter used to be total bad-ass and awesome, until Matt Ward fucked up the awesomeness and replaced it with massively retarded shit. (Deep Striking land raiders!HURR!)
In times of dire need, they are helped out by the Sanguinor, a guy who seems to be a Blood Angel except more literally so. Maybe he's some psychic manifestation of the chapter. Maybe he's a ghost of Sanguinius. Nobody knows. The important thing is that he enjoys piledriving bloodthirsters from space.
Death Company
The "Death Company" is a group of Blood Angels who were afflicted by a mutation in their gene seed known as "Black Rage". This is where they see themselves as Sanguinius battling Horus in his battle barge. Long story short a marine afflicted with "Black Rage" will be almost as Angry as Angry Marine except that they can't control themselves and so if they aren't killed, they are locked away as they're too batshit insane to be controlled. While they are in battle though, a Death Company marine is just as fearless as an Angry Marine and charges into a group of enemies in a pure display of valor, devotion to the Emprah and Sanguinius and most importantly RAAAEEEGGG.
Unfortunately due to 5th edition codex dickery, Death Company can be led on a merry goose chase as they try, desperately, to kill a lone speeder, while the rest of the army dies because half of it is failing at tag with Eldar.