It's a piece of parchment with letters written in blood. It was written with painstaking care.
"I, Commander Ferrows of the Second Column, do vow that I have never willfully written a traitorous line in my life. I was forced to write letters... terrible letters that will get many good men killed. But I could not control my hands!
I also never gave up Council secrets. They were ripped from my head!
Dalvos has left now. He said that my brain is too pathetic to be used in his creations, but I know the truth. This is revenge. I am to watch my men die horrible deaths because of what the Council has done to his family. I lay the blame for this at the feet of Jarmanger himself!
There are additional scribblings, but the letters become fainter, as if the author didn't apply enough pressure to the parchment. You can make out a few words: "Jarmanger must...", "General Lavorel will..." , "cave network beneath Eltibule Keep."