  Nova eruptions, thermonuclear explosions on the surfaces of white dwarfs
(WDs), are now recognized to be among the most common shock-powered transients.
We present the early discovery and rapid ultraviolet (UV), optical, and
infrared (IR) temporal development of AT 2019qyl, a recent nova in NGC 300. The
light curve shows a rapid rise lasting $\lesssim 1$ day, reaching a peak
absolute magnitude of $M_V = -9.2$ mag, and a very fast decline, fading by 2
mag over 3.5 days. A steep drop-off in the light curves after 71 days and the
rapid decline timescale suggest a low-mass ejection from a massive WD with
$M_{\mathrm{WD}} \gtrsim 1.2 M_{\odot}$. We present an unprecedented view of
the early spectroscopic evolution of such an event. Three spectra prior to the
peak reveal a complex, multi-component outflow giving rise to internal
collisions and shocks in the ejecta of an He/N-class nova. We identify a
coincident IR-variable counterpart in the extensive pre-eruption coverage of
the transient location, and infer the presence of a symbiotic progenitor system
with an O-rich asymptotic-giant-branch donor star, as well as evidence for an
earlier UV-bright outburst in 2014. We suggest that AT 2019qyl is analogous to
the subset of Galactic recurrent novae with red-giant companions such as RS Oph
and other embedded nova systems like V407 Cyg. Our observations provide new
evidence that internal outflow collisions likely play an important role in
generating the shock-powered emission from such systems.
