Drop a stone into a pool and watch the ripples spread out.
The prince saves the princess and they marry. But then they have a daughter, and perhaps the faeries are still interested. A saint raises the dead and stops a war, and years later the wealth of the pilgrimage site nurtures a hive of diabolists. A maga recovers a mighty enchantment, and her apprentice accidentally opens a gate to a regio.
Actions have Consequences.
This Ars Magica book contains five sequences of three stories each: issues and situations that cannot be fully resolved in a single story, but which return to draw the characters back in years later. Divine, Infernal, Faerie, and Magic: thematic threads for the tapestry of your saga.