: Do we have a verdict on this... Who was Phelot working
: for at Avon's Grove back then?
Shiver is the most likely candidate, as Avon's Grove lies pretty squarely along the route of her march.
That said, Shades seem to have been given at least some degree of tactical flexibility, and have sometimes been seen leading contingents separated from the main body of the army of their patron Fallen Lord (as was the case with Sinis and the Shade who was left to hold Muirthemne during the war against Soulblighter, and whose name I can't remember).