Black Screams is a War Letter from the Bright Lord DLC.
Below is a transcript of the letter;
We started shouting in the dark, trying to scare 'em off. We'd scare one off, but two would come back, then the shouting would stop and the screaming would start. Then the screaming would stop and the sounds would get real bad.
Chewing and crunching, through armor, through flesh, through bone. It was so black down there we couldn't see the blood, but we smelt it.
When we thought we couldn't take it any more, they poured down the liquid fire... then we could see, we could see it all and i'll never forget it. A hundred and twenty went down. And i came out!