The ESSENCE Supernova Search found nearly 200 type Ia supernovae over a 6-year search and is currently analyzing the cosmological results. But it also discovered a handful of odd transients including the outburst of a luminous source named Y-155. Believed to be at a redshift of z=0.8, Y-155 would be the most distant explosion found by the ESSENCE search. Spectra show broad absorption features with expansion velocities consistent with a supernova, but the identification of the features remains uncertain. The extreme luminosity implies the death of a very massive star or an unusual outburst from an accreting super-massive black hole. Other speculations are welcome.