Dark Matter could reside in a hidden sector with gauge structure similar to the Standard Model. In particular, the hidden sector may include a non-Abelian gauge interaction with confinement scale around 100 MeV, similar to our QCD. Dark mesons, counterparts of the usual pions, kaons etc., can then play the role of dark matter. Such particles may experience strong number-changing self-interactions, similar to the 2K<->3pi scattering familiar in QCD. Intriguingly, such self-interactions can naturally produce a thermal relic abundance of dark mesons consistent with observations. In this talk we will explore two variations of this basic scenario, “Strongly-Interacting Massive Particle” (SIMP) and “Elastically-Decoupling Relic” (ELDER). We will discuss the basic features of each scenario, explicit models in which they may be realized, and their experimental signatures.