This paper presents Monolith, a high bitrate, low- power, metamaterials surface-based Orbital Angular Momentum (OAM) MIMO multiplexing design for rank deficient, free space wireless environments. Leveraging ambient signals as the source of power, Monolith backscatters these ambient signals by modulating them into several orthogonal beams, where each beam carries a unique OAM. We provide insights along the design aspects of a low-power and programmable metamaterials- based surface. Our results show that Monolith achieves an order of magnitude higher channel capacity than traditional spatial MIMO backscattering networks.