Faerie Ring are strange for many reasons, not the least of which is their ephemeral nature. One evening they are there, all singing and dancing, prancing and mincing, and the next they are gone.
Powers
Hiding - A Faerie Ring can create an extradimensional refuge in the ground within its space which lasts 1 hour. The space can hold as many as eight Medium or smaller creatures.
Transport - Some, perhaps it's only those touched by the Fey, have the power to move from one circle to another over great distances. This is a power possessed by Reidoth the Druid and perhaps others.
Gifts - When the spirit takes non-faeries and they dance with the fey music they will find that they cannot stop dancing until dawn. Those who dance the whole evening will generally be granted a boon, some enchanting flower petal shoes, or bells; perhaps even a bag of fey gold.