Genderless (seemingly alien) being speaking with flat intonation.
The characters heard its voice telepathically at the beginning of the Act I Prologue. In its effort to probe their minds (“identify the nature of the interference… commence probing”), it discovered that their memories had been erased (“They don’t know who they are… wake up, wake up, if you can’t remember—”).
In the Act I Epilogue it attempted to contact the party again. Instead of searching through their conscious and unconscious minds, it tried to search for their memories via their subconscious connection to the Dimension of Dreams. In the process, it stirred up shared memories of meeting the Stranger.
In the Act II Prologue, it was in a dark cell bemoaning its fading connection to the PCs. Chained by the neck, wrists and ankles, sitting in its own waste, it was in agony and fearing its own death—a concept nearly unfathomable for it considered dying to be the greatest crime it could possibly commit against its own species. It had just reached out to the PCs and failed to connect through the moment of their births as individuals—instead finding only memories from their later childhoods. It instead attempted to locate them by means of another birth. But then its connection to the characters was cut as they left Briarstone Isle behind.
First Reference: Act I Prologue
Other Notable References: Act I Epilogue, Act II Prologue, Chapter 44