"She doesn't have to die..." - The Angel's message
After Dr. West attempted suicide through a Laudanumoverdose because his wife had died, he spoke with an angel at "the threshold to the eternal abyss". Accordin to Dr. West, the angel's face was "a pale mask of serenity". The Angel told Dr. West of how he could bring Leonora back to life before Dr. West woke up. At first Dr. West believed the Angel was just a hallucination, until he used the Angel's knowledge to resurrect Leonora.
Because both the "angel" and the Terror Mask share the line "She doesn't have to die" (as especially heard in Phase Nine), it's possible that it was actully the Terror Mask that spoke to Dr. West. It's possible that driving Dr. West insane might have been part of it's revenge scheme.