  The Time-Domain Extragalactic Survey (TiDES) is focused on the spectroscopic
follow-up of extragalactic optical transients and variable sources selected
from forthcoming large sky surveys such as that from the Large Synoptic Survey
Telescope (LSST). TiDES contains three sub-surveys: (i) spectroscopic
observations of supernova-like transients; (ii) comprehensive follow-up of
transient host galaxies to obtain redshift measurements for cosmological
applications; and (iii) repeat spectroscopic observations to enable the
reverberation mapping of active galactic nuclei. Our simulations predict we
will be able to classify transients down to $r = 22.5$ magnitudes (AB) and,
over five years of 4MOST operations, obtain spectra for up to 30,000 live
transients to redshift $z \sim 0.5$, measure redshifts for up to 50,000
transient host galaxies to $z \sim 1$ and monitor around 700 active galactic
nuclei to $z \sim 2.5$.

Instrumentation and Methods for Astrophysics