The Multiverse, which consists of several universes, many layered dimensions, spheres and alternate worlds, is the place where the eternal struggle between Law and Chaos, the two main forces of Moorcock's worlds, takes place. In all these dimensions and worlds, these forces constantly war for supremacy. But the victory of either Law or Chaos would be disastrous for mankind, and therefore the Balance needs to work for, unsurprisingly, balance.
The Eternal Champion, a Hero who exists in all dimensions, times and worlds, is the one who's chosen by fate to fight for the Balance - but he often doesn't know of his rôle, or, even worse, he struggles against it, never to succeed.
All the incarnations of the Eternal Champion are facets of each other.
Some of the incarnations of the Eternal Champion include: