What do you want it to do?
I think that maybe the mages out there, from time to time, need to hear what seems obliviated to muggles: that open minded, self aware thinking should supersede the institutional interpretation. People are told something can't be done. Then they are rewarded or punished according to their acceptance of the false axiom. Then you have a religion that wants to burn psychic healers and call itself a Tea Party, so that the founding fathers can spin in their graves.
Anything is possible, pretty much, but since we live in an Universe, that means that everything that is created within it has to enjoy some kind of harmony.
Power is the ability to do work, and work always involves some form of service to other beings. What some people think is power is just personal influence, which divorced from service forms a heavy crust that drags a person down like a guy who drowns because he tries to swim a river with too much gold in his pockets, usually in harmful pursuit of someone with less gold.
Anything that can be imagined can be created, somewhere. It is like a prop in the attic of an opera house, waiting for the right production. The trick is writing the opera that will form a sustaining barrier between the desired thing and the context reality that will eventually dissolve it.
There are props for Terry Gilliam films that will have never been seen before or since. No wonder J. Rowling wanted him as first pick for a director. Is there a double decker prairie schooner that was part gypsy wagon and part performance stage? As soon as someone builds one, yes. Not getting it stripped will be a matter of what neighborhood one from which one refrains from entering, I guess.
A magic ring would have to be able to recruit unseen powers. One would have to understand such powers in terms of their abilities, and the compensation they would require for their cooperation. Otherwise, it could be somewhat taking a job with the mob and never being heard from, again.
So, not to sound preachy but, the craft of witches is so often more about learning what and whom a magic user may trust, and under what conditions, rather than producing effects which might prove vain or volatile. For example, the art of making fireworks in Italy is centuries old. But, there are always risks involved. So, knowing that anything is possible, if one is wise, one has to ask oneself, how much is this going to cost me?