Complex sentence: In this year fierce, foreboding omens came over the land of the Northumbrians, and the wretched people shook; there were excessive whirlwinds, lightning, and fiery dragons were seen flying in the sky.
Split into simpler sentences: In this year fierce, foreboding omens came over the land of Northumbria. There were excessive whirlwinds, lightning storms, and fiery dragons were seen flying in the sky.