Complex sentence: Gandalf tells them that Merry and Pippin are safe, and the four ride to Rohan's capital Edoras, where Gandalf rouses King Théoden from inaction against the threat Saruman poses.
Split into simpler sentences: Gandalf tells them that Merry and Pippin are safe, and the four ride to Rohan's capital Edoras. There Gandalf rouses King Théoden from inaction against the threat Saruman poses.