  We describe the design and performance of a magnetic bottle electron
spectrometer~(MBES) for high-energy electron spectroscopy.
  Our design features a ${\sim2}$~m long electron drift tube and electrostatic
retardation lens, achieving sub-electronvolt (eV) electron kinetic energy
resolution for high energy (several hundred eV) electrons with close to 4$\pi$
collection efficiency.
  A segmented anode electron detector enables the simultaneous collection of
photoelectron spectra in high resolution and high collection efficiency modes.
  This versatile instrument is installed at the TMO endstation at the LCLS
x-ray free-electron laser (XFEL).
  In this paper, we demonstrate its high resolution, collection efficiency and
spatial selectivity in measurements where it is coupled to an XFEL source.
  These combined characteristics are designed to enable high-resolution
time-resolved measurements using x-ray photoelectron, absorption, and
Auger-Meitner spectroscopy.
  We also describe the pervasive artifact in MBES time-of-flight spectra that
arises from a periodic modulation in electron detection efficiency, and present
a robust analysis procedure for its removal.
