This work unit proposes to construct a cold indirect geometry time of flight spectrometer for performing inelastic neutron scattering experiments optimized for optimal efficiency in the horizontal scattering plane at the European Spallation Source. A horizontal geometry is chosen for compatibility with performing neutron scattering experiments under extreme conditions. The instrument concept is called the Continuous Angular Multiple Energy Analysis Spectrometer, CAMEA. In this report we will outline the science case for CAMEA, highlighting the science that could be performed on CAMEA, the demand for an instrument of this type, aswell as identifying the current and future technology in neutron scattering that can be utilized. The basic concept of CAMEA is to maximize neutron count rates for scattering in the horizontal plane, with a quasi-continuous angular coverage of the scattered neutrons. High neutron detection efficiency will be obtained by using banks of concentric analysers placed behind each other, analysing different neutron energies of the scattered neutrons. Optimization of a horizontal scattering geometry has been chosen to be compatible with extreme sample environments and the ability to perform inelastic neutrons scattering studies. We will highlight how this provides a generation of advancement in inelastic neutron scattering under extreme environments, and what new possibilities for scientific studies CAMEA enables in inelastic neutron scattering.