CovenantJr wrote:As I've mentioned before, my theory is that white gold controls wild magic in a form specific to its weilder; I can't see Roger's white gold (if he had decided to buy some) being of quite the same nature as TC's. That also makes sense (to my mind, at least) in the context of what Roger/Foul are trying to achieve in Runes. Covenant is now part of the Arch of Time, one with wild magic. I suspect only his "type" of wild magic would be effective against him now.
Still, remember that by the end of WGW, Covenant (or more appropriately, his spirit) was repeatedly attacked with wild magic by Foul himself, and although he suffered, he couldn't be defeated... while different wielders probably exert different degrees and varieties of power, I doubt there are different types of wild magic (because that would imply a form of order codified by some sort of law). It is rather probable, instead, that Joan's ring is useless because she is a tool of the Despiser, and therefore even if Roger or Foul himself wielded it, it would be powerless to destroy the Arch of Time (even if you don't count Covenant's guardianship).
I believe Roger knew all along who had his father's white gold ring (Foul probably suspected it, since Linden was the only one left in the room when he disappeared, in WGW)... he asked Linden only in hopes that she would give it to him freely, thus making sure it wasn't a simple tool.