  We present the discovery and high-cadence follow-up observations of SN
2018ivc, an unusual Type II supernova that exploded in NGC 1068 (D=10.1 Mpc).
The light curve of SN 2018ivc declines piecewise-linearly, changing slope
frequently, with four clear slope changes in the first 30 days of evolution.
This rapidly changing light curve indicates that interaction between the
circumstellar material and ejecta plays a significant role in the evolution.
Circumstellar interaction is further supported by a strong X-ray detection. The
spectra are rapidly evolving and dominated by hydrogen, helium, and calcium
emission lines. We identify a rare high-velocity emission-line feature
blueshifted at ~7800 km/s (in Ha, Hb, Pb, Pg, HeI, CaII), which is visible from
day 18 until at least day 78 and could be evidence of an asymmetric progenitor
or explosion. From the overall similarity between SN 2018ivc and SN 1996al, the
\Ha{} equivalent width of its parent HII region, and constraints from
pre-explosion archival Hubble Space Telescope images, we find that the
progenitor of SN 2018ivc could be as massive as 52 Msun but is more likely <12
Msun. SN 2018ivc demonstrates the importance of the early discovery and rapid
follow-up observations of nearby supernovae to study the physics and
progenitors of these cosmic explosions.
