Endless Shadow is a War Letter from the Bright Lord DLC.
Below is a transcript of the letter;
Description[]
We are going to crush those softskins utterly, no matter how many walls they hide behind. Their time is at an end. Our time is come.
The Shadow can't be defeated, it can't be banished, it can only grow and grow until it covers the whole world.
The puny kings of Men, of Elves, of Dwarves. If we let 'em live at all, it's only going to be to serve us, to let us enjoy the misery in their eyes.