Board Thread:Planning/@comment-4844180-20130721230302/@comment-5135903-20130723215136

Why not femtorobots constructed from some form of degenerate matter (like neutronium, or more likely AB-matter). They would be much smaller than nanorobots and would be able to pass through ordinary matter, making them harder to detect. They would also be a lot tougher (due to the strong force) and denser, which would make them better suited to achieving their job of gravitationally slowing the expansion of the universe.

Not to mention the fact that femtorobots are more advanced than nanorobots, providing a better representation of the (I presume) high advancement of the civilization that created them.