The Authority is a superhero RPG based on The Authority comic by Warren Ellis and Bryan Hitch. The rules use the Tri-Stat system, but the rulebook also is compatible to the d20 System, especially to Silver Age Sentinels d20.
The theme is usually that of grand scale menaces and god-like heroes and villains. The base of the original Authority team for example is a spaceship 50 miles wide and 35 miles high. The adventures involve space and inter-dimensional travel (and dangers), wars between countries and whole worlds, destruction of cities, etc.