Complex sentence: Westley, Inigo, and Fezzik invade the castle, prompting Humperdinck to order a drastically abridged version of the wedding ceremony, after which he rushes Buttercup to her chambers and locks her in.
Split into simpler sentences: Westley, Inigo, and Fezzik invade the castle, prompting Humperdinck to drastically abridge the wedding ceremony. Then he rushes Buttercup to her chambers and locks her in.