What is the Harbinger?

Being teased since the very beginning of our heroes journeys, the Harbinger has been an elusive being/creature/thing for our party. Perhaps it was the shadowy figure that haunted them throughout their time in Eldertree Haven.      The party now finds out after visiting the ritual room behind the waterfall at Veiled Serpent's Lake that the Harbinger wasn't a person or a creature, instead a weapon that is fragmented and interlinked with the souls of 4 creatures/people. One of them being Jade. How this will unfold only time will tell...