RPers of Space Marine II, What's your Marine's story?

Title. I figure a few people have to go beyond cosplaying as their preferred/favorite chapter but also came up with a name and backstory for who they really are. And with how 40k is, it's not unreasonable whatsoever to wanna RP as, say, a Salamander who fought in the 13th Black Crusade, a Blood Angel whose first action was against the Tyranids on Baal itself, a Mortificator who fought on Tarsis Ultra, and so on.

Me personally, I don't go too much into it but I like to think my Devastator (I refuse to call them "Heavies", fight me) served with this angry, nihilistic, bitter traitor and has dedicated the rest of his life to making up for the stain on the honor of the chapter that his sergeant left.