Epics are used to get a bigger picture of user stories, but we need another level of abstraction. We need to bring together the various Epics that describe how our solution will evolve to its final endpoint, and how different functional teams and specialists will interact.
This article by Ross Hall introduces the Saga, which is more than a new term to describe an Epic of Epics. A Saga demands a more strategic mindset that is as concerned with the journey as the end state. Consider the Saga not as a means of describing a piece of functionality to be delivered now, but rather an expansive tale that explains how, over the next few years, the business strategy is going to unfold and how everyone will play their part.