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Dusty quasars might be in a young stage of galaxy evolution with prominentquasar feedback. A recently discovered population of luminous, extremely redquasars at $z\sim$~2--4 has extreme spectral properties related toexceptionally powerful quasar-driven outflows. We present Keck/KCWIobservations of the reddest known ERQ, at $z=$\,2.3184, with extremely fast[\ion{O}{III}]~$\lambda$5007 outflow at $\sim$6000~km~s$^{-1}$. The Ly$\alpha$halo spans $\sim$100~kpc. The halo is kinematically quiet, with velocitydispersion $\sim$300~km~s$^{-1}$ and no broadening above the dark mattercircular velocity down to the spatial resolution $\sim$6~kpc from the quasar.We detect spatially-resolved \ion{He}{II}~$\lambda$1640 and\ion{C}{IV}~$\lambda$1549 emissions with kinematics similar to the Ly$\alpha$halo and a narrow component in the [\ion{O}{III}]~$\lambda$5007. Quasarreddening acts as a coronagraph allowing views of the innermost halo. A narrowLy$\alpha$ spike in the quasar spectrum is inner halo emission, confirming thebroad \ion{C}{IV}~$\lambda$1549 in the unresolved quasar is blueshifted by$2240$~km~s$^{-1}$ relative to the halo frame. We propose the inner halo isdominated by moderate-speed outflow driven in the past and the outer halodominated by inflow. The high central concentration of the halo and thesymmetric morphology of the inner region are consistent with the ERQ being inearlier evolutionary stage than blue quasars. The\ion{He}{II}~$\lambda$1640/Ly$\alpha$ ratio of the inner halo and the asymmetrylevel of the overall halo are dissimilar to Type~II quasars, suggesting uniquephysical conditions for this ERQ that are beyond orientation differences fromother quasar populations. We find no evidence of mechanical quasar feedback inthe Ly$\alpha$-emitting halo.

Probing the Inner Circumgalactic Medium and Quasar Illumination around the Reddest `Extremely Red Quasar' (ERQ)