In Chapter 173, upon arriving at the Mysterium, Bash, Grip, and Pandora received communication directly from the Prisoner, while they were fully conscious:
“The touch of ruin, of madness, is upon this place. More than the Blot. Many gather in the Tapestry of this Chaos. That which Should Not Be has been birthed within. This place is poisoned. But you already know this. Hurry—you must staunch the wound!”
This identical message was heard by Stazi, Stanhope, Tharivol, and Nheb shortly after entering the Mysterium in Act IV Interlude Part 2.
First Reference: Chapter 173
Other Notable References: Act IV Interlude Part 2