The quote on the wall of the cellar comes from the Bible, the book of Daniel, chapter 5. Someone of the Reds had a macabre sense of irony...Belshatzar (Balthazar) was a weak (and the last)Babylonian king (coregent of his father, Nabonidus), and died when Babylon was taken by the Persians, in 539 BC. Apparently, he was killed by his servants...
I wouldn't be surprised if it was Yurovsky who wrote it.