The first observation of the ${\mathrm{\ensuremath{\Omega}}}_{b}^{\ensuremath{-}}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Xi}}}_{c}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{\ensuremath{-}}$ decay is reported using $p$ $p$ collision data at center of mass energies of 7, 8, and 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of $9\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. Four excited ${\mathrm{\ensuremath{\Omega}}}_{c}^{0}$ baryons are observed in the ${\mathrm{\ensuremath{\Xi}}}_{c}^{+}$ ${K}^{\ensuremath{-}}$ mass projection of the ${\mathrm{\ensuremath{\Omega}}}_{b}^{\ensuremath{-}}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Xi}}}_{c}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{\ensuremath{-}}$ decays with the significance of each exceeding five standard deviations. They coincide with the states previously observed in prompt $pp$ and ${e}^{+}{e}^{\ensuremath{-}}$ production. Relative production rates, masses, and natural widths of the states are measured, and a test of spin hypotheses is performed. Moreover, the branching ratio of ${\mathrm{\ensuremath{\Omega}}}_{b}^{\ensuremath{-}}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Xi}}}_{c}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{\ensuremath{-}}$ is measured relative to the ${\mathrm{\ensuremath{\Omega}}}_{b}^{\ensuremath{-}}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Omega}}}_{c}^{0}{\ensuremath{\pi}}^{\ensuremath{-}}$ decay mode and a precise measurement of the ${\mathrm{\ensuremath{\Omega}}}_{b}^{\ensuremath{-}}$ mass of $6044.3\ifmmode\pm\else\textpm\fi{}1.2\ifmmode\pm\else\textpm\fi{}1.{1}_{\ensuremath{-}0.22}^{+0.19}\text{ }\text{ }\mathrm{MeV}$ is obtained.