  The last decade has seen the rapid, concurrent development of new classes of
energetic astrophysical transients, including Fast Radio Bursts, Superluminous
Supernovae, and ultralong gamma-ray bursts. We consider the implications of an
emerging consensus on the origin of these diverse phenomena as different
signatures of magnetar birth. We describe how magnetar-powered radio transients
from milliseconds to gigaseconds will be used to address diverse physical
questions related to the stellar evolution and death, the circum- and
intergalactic medium, and fundamental physics on scales ranging from the
quantum to cosmological. We argue that high-sensitivity radio interferometer
concepts in development will be critical to accessing this science. There is
also a growing need for scientists with expertise in new statistical tools and
software techniques.
