For physical reasons one expects that many spacetimes will eventually settle down to a stationary state. In many cases the final equilibrium configuration will be a black hole. Mathematically it has been shown in 70s that under broad assumptions in an empty spacetime with a single black hole the equilibrium state is a Kerr solution. Over the years some progress has been achieved in extending this black hole uniqueness theorem in various directions. However many challenges still remain and new challenges are surfacing. In this talk we mainly focus on the question of multiple black holes wherever uniqueness results have been established with the assumption of a single black hole. A technique inspired by Schoen and Yau's positive mass theorem appears to be powerful in this field. We use it to solve another problem that remained unsolved until last year. It is the uniqueness of magnetized Schwarzschild solution without the assumption of a single black hole.