He dropped for me something simply named "lemon" but my inventory was full, and I never found it. Don't know anything about it, or even if its of any value whatsoever.
GoA have confirmed that as per ver 1.88 on European servers (Dyvet anyway) the weapons Vile and Umbrage do NOT drop from this mob. Now I can stop killing him after doing it 40 times.
Pretty sure this is bugged on European servers (Dyvet cluster). The Rock Creatures do not activate. All he does is throw a weed field around you (which doesn't do anything nasty). He then dropped a otd (the cloak) but I have not been able to get him to drop Vile or Umbrage. These may ofc be Alb weapons only.