Complex sentence: Bluebeard seems terrifying but the secret is that his beard is fake when Ludwig is accidently mistaked for one of Bluebeard's wives and he claims to have another personality when putting on the beard.
Split into simpler sentences: Bluebeard seems terrifying, but the secret is that his beard is fake. When Ludwig is accidently mistaken for one of Bluebeard's wives, Bluebeard claims to have another personality when putting on the beard.