This could occur within the laws of physics, albeit a corner case of them which is typically not given much credibility because it offers fantastical possibilities for which we have little to no evidence for.
The laws of entropy really only take hold when you forget information. Many constructs built around reversible computing specifically avoid erasing bits of information so that they can be returned to their previous state after the calculation is done. This construct legally sidesteps entropic losses, if you could actually build one.
The reason entropy always "wins" at our level is that we very rapidly "forget" the result of collisions between molecules. We treat them as "random events," which means we lose a little information every time they occur simply because we're not tracking them 100%.
What if something was tracking them?
If you had an entity which could track the results of those collisions, it could do some pretty amazing things. It could be thought of as a ghost, or it could be thought of as some exotic field, but the result would be the same. Every "random" collision we think we observe may actually be carefully planned, and thus not random at all. We just don't know the key to unlock the "randomness" and realize that there's a pattern to it.
All of science would be justified in believing that these collisions are random and that the entropy of the system has increased with each collision, but they'd be wrong. All that information would be retained by this entity, usable for exotic things like suddenly making all the air molecules in the room move to one side of the room. Statistically, it is highly improbable that it will occur, if the air molecule movements are "random." However, if we know a-priori that there is a structure to their "randomness," it becomes a lot more plausable.
It would be hard for any entity to merely "remember" those trillions of collisions every moment; however, if it were to interact with the system to encourage those collisions to occur in a way which is highly compressable, in the data sense, it may be able to keep track of far less information (so long as it can keep the whole system coherent).
For such a system, crypmancy would be easy. You would merely beseech this entity to freeze something for you, and it would kindly take away all that "heat" that is actually particle motion between particles whose positions are know to it (but not to science). It would appear that entropy would be decreasing when you do so, but in reality all that would be happening is you would be having to update your estimate of how much entropy is in the system in the first place. Entropy would still be increasing, you'd just see the illusion of it decreasing.
There would be a lower bound to this if there is any actual indeterminism in the world. If the classical observations of quantum mechanics are truly random as they are in the Copenhagen interpretation, this entity would be in a constant fight with QM to maintain that detailed structure of the universe while making sure the structure is too advanced for us humans to recognize. However, some of the other interpretations may suggest that entity could step beyond our universe, and be in a position to manipulate the quantum waveforms directly.
Not impossible by the laws of physics. Improbable, but then again, what do we know about the probabilities of our own existence?