Bonesmaster?

[Mah Al Ibara]

I searched and could find no posts about this, which seems odd. When you first set out on the Dark River, you can go north for a short distance and make landing at a place where a seemingly invulnerable "Bonesmaster" repeatedly calls forth "Dancing Bones". I've killed the first two batches and am on the third, but I thought I'd ask for advice here before putting much more time and energy (literally) into this spot. This is my second time through the game, and I'm embarrassed to admit that I can't recall how I handled this the first time. I may have just given up and left. Does the Bonesmaster become vulnerable after you'll killed enough Dancing Bones? What can you get from this spot? Any valuable item to be had here?

[Mah Al Ibara]

Answering my own question. Midway through the third batch of Dancing Bones, Bonesmaster (who has been standing motionless till now) "decides to eliminate the intruder," and attacks, at which point he becomes vulvernable. In my case, he went after my priest, and though he seems to be able to attack only one character per turn, he does a lot of damage per hit, so make sure you're properly beefed up, and don't let your priest die, since the "Repel Spirit" spell is the most effective attack. Don't waste your mage's energy attacking the Bonesmaster with "Lightning Spray" or anything higher, since you can do plenty of damage with a simple "Bolt of Fire." What you get for your trouble is "Deadeye Chain" (12.5 lbs., Armor +22%, +20% Stun Resistance, -5% hit chance, +5 to Sharpshooter, 10% fatigue removal, Value 2000 coins.)