The mystery will be what its eating and what it is pooping
My ol pal Pythagorus mused about the music of the spheres obeying a 12 note scale. While wrong he was kinda right if you consider string theory vibrations in 12 dimensions. Even Einstien got esoteric in his last 30 years and spoke of the 'mind of god' being virtually alive.

I've heard how dark matter is like the branches and trunk of a tree while normal matter is like the leaves on the cosmic tree but I never heard that the diet of dark matter is visible matter.

Dark matter may be eating some of those 12 dimensions that are causing in turn the acceleration of the universe. A star trek cure for the universe might be to sour the 'taste' of the devoured dimension and protect sections of the universe from tearing apart. Perhaps your Overlords are big fat gluttons.