I didn't seen an obvious solution to the Prince of Bones either, to be honest. The illusion of him Masego was providing made it clear why: we were dealing with, essentially a corpse encased in what had to be a few hundred pounds of steel. It looked like armour, but it wasn't. Just layers upon layers of metal, moved by the necromancy buried safely deep within. Worse, that steel was layered with enchantments and whatever devilries the Dead King could muster. Running away wasn't usually an issue, the Prince was slow on the move, but when you couldn't run? Even the Pilgrim hadn't been able to put him down, and the man had a Choir whispering tricks in his ear.

...

“Sold,” I said. “Mirror Knight for the Prince of Bones?”

“There’s no one else who would be able to take a hit from him,” the White Knight replied. “Who to pair him with is the issue. I would argue against a full band here.”

The Barrow Sword, I saw, was watching us both like a starving hound being shown into a larder. Why? After a moment I realized that even as I thought the question, Ishaq had asked it out loud.

“Because Hanno doesn’t think we can kill the Prince of Bones,” I said, “which means investing a full band there would be a waste. A partner, though, is pretty much a precaution to keep the Mirror Knight alive.”

- Book 6, Chapter 75: Desolation