Sanguinary Priest

By Sanguinius, you will drink this cup and become as pretty as me!

The Blood Angels are a little weird, so they call their Apothecaries Sanguinary Priests. There's a lot of weird blood rituals they do.

Also, they LITERALLY carry the blood of Sanguinius (How much blood Sanguinius would have before being completely drained from his already dead-beyond-dead body is unknown, although cell cloning of his blood might be a reasonable theory), since they're injected with a sample of it when they become Sanguinary Priests. This means they are the prettiest Marines, as they look the most like Sanguinius.

They also have taken over the role of normal space marine Chaplains in the spiritual guidance of their Battle Brothers. Where Chaplains only care for Blood Angels fallen to the Black Rage, Sanguinary Priests care for the spiritual needs, lore of the chapter and try to manage the red thirst, doing their best to curb its effects, or when the battle turns against them - harness it as a weapon against the enemy.

Sanguinary Priests also oversee the induction of new recruits into the chapter, by a process known as Insanguination. During the Insanguination, geneseed is implanted into successful Neophytes by drinking from the Blood Chalice held by a Sanguinary Priest. Because of this role, the Sanguinary Priests are responsible for the care of the Red Grail, the chalice holding the blood of Sanguinius himself. This blood is regularly circulated through the veins of the Sanguinary Priests, who are injected with a sample from the Grail, then later cut themselves to bleed it back in. In this way, the blood is continuously kept fresh, and every single draught from the Grail contains a small percentage of the original blood of the Primarch....yeah we told you that it is a weird ass ritual.

Sanguinary Priests are armed almost the same as a regular Apothecary but they also wield a Chainsword, wear Artificer Armour and a Blood Chalice which is the chalice containing Sanguinius' pretty little blood. Although how the Priest can go into battle effectively with what fields as practically a giant metal cup is unknown (Bonking the heads of Heretics Demoman-style (although that would probably break the chalice) maybe?).