D&D General How would you make "finding out how to break the spell" interesting?

I think this depends on what sort of things your players find interesting. Personally, as a player, I don’t find it very interesting to “work out” (i.e. guess) what the DM has in mind and am more interested in declaring actions for my character and, as long as those actions are permissible, having them have a reasonable chance of success with the information I’m given. So, if your players are anything like me, my suggestion would be to hold on loosely to your ideas about the ritual and to follow the players’ lead in conducting their research, if that’s what they choose to do. As for running a minigame around that, I don’t have any experience with this, but I’ve gathered that 4e skill challenges might be applicable.