So just because, I decided to steal the idol from the druids in the midst of their ritual. Never really bothered with it before during the ritual and wanted to see what happened. Firstly, so far, they have failed to notice it is gone. The ritual continues unabated despite it supposedly being needed for said ritual. Second, while the idol did for awhile continue to give off the aoe and grant the party the blessing as I carried it around, it eventually stopped doing so. At this point it has become just a shiny decoration in my camp. It still ha the green shine on it but lacks the aoe blessing.