When a human goes to kiss his hand he gets a quick warning from Ruel to mind the ring, which is as sharp and cutting as she meant it to be. 'She' being his wife. The relationship between Ruel and his mate is more fraught than occurred between King Thranduil and his queen. The ring is the first hint that all is not as it seems in the Fated relationship.
This ring is as close a duplicate to Ruel's as I could find. Its stone is stormy, and it is, in shape, a lot like a thorn. It's one of the several he owns and wears, but this ring would probably have the most meaning to him, of all the jewels that he owns or inherited from his father. The milder, milkier twin, with more curving shapes would belong to his wife.