…We had a game where one player had 11 points, and another had 10 including a Magic Ring. Could they use the Magic Ring on a player who did not declare victory, to try to get their points up higher than the person with 11?
A: The FAQ in the rules reads: “Once someone has declared victory, it’s too late to use a Magic Ring on them.”
Really, it should be amended to read… “(or on anyone else, for that matter.)”
Strategically, you should always use a Magic Ring as soon as you get it, since there’s no advantage to holding it until later, only the risk that someone will declare victory before you declare your intention to use it.
See also What if someone uses a Magic Ring while other players are still counting up their points?