  A space-based interferometer operating in the previously unexplored mHz
gravitational band has tremendous discovery potential. If history is any guide,
the opening of a new spectral band will lead to the discovery of entirely new
sources and phenomena. The mHz band is ideally suited to exploring beyond
standard model processes in the early universe, and with the sensitivities that
can be reached with current technologies, the discovery space for exotic
astrophysical systems is vast.
