I remember that the guy said to go to the Low Forest into the High Forest into the Gloomy Forest into the Greengrove. Easy. And indeed I went from the Low Forest into the High Forest into the Gloomy Forest into the Greengrove. Slight problem, though -- I couldn't seem to find any damn druids in the Greengrove. And I recalled specifically being told to go to the Greengrove.
Well, I wasn't one to give up that easily. MAYBE the druids were really a zone further in this welcoming cave:

They must have been evil druids, though -- even their head druid didn't want to talk and he had a really scary name. I figured maybe he'd surrender at low health and I popped all sorts of buffs and potions to manage to win.

Alas, no cherries were to be found and I left the cave despondent.
In desperation, I returned to Aron's shop to refresh my memory on the directions.

I decided to ignore the "leading to Greengrove" part (since I had already thoroughly searched the Greengrove) and worry about the "find a cave in the Gloomy Forest" part.
Lo and behold, I found the druids in a zone that was NOT called Greengrove and NOT leading to Greengrove either!

I beseech ye to change at least a little bit of this so that people aren't confused in the future. Because most people aren't going to be able to solo Xumbar the Terrible.
Which also led to the druids thanking me for doing a quest I had never received when I met them possessing Xumbar's head. Fortunately, I was able to place the head on the ground temporarily to see what the druids' story was and why they wanted Xumbar's head.
Still, a rather weird turn of events.