We discuss a new dark matter framework, Elastically Decoupling Relics (ELDER), and its phenomenology. We then discuss multi-messenger astrophysical probes of various dark matter scenarios, utilizing electromagnetic emission and gravitational signatures from neutron star mergers (and black hole mergers with the gravitational wave signature) to probe super-heavy (PeV - EeV) asymmetric dark matter. Finally, we discuss how to use intensity-frontier experiments to investigate weakly coupled states, including dark scalars, dark photons, heavy neutral leptons, and millicharged particles.