A monster that actually swallowed a German WWII airplane? Yes, please!
Rumors of a strange, giant creature living in Lake Brosno have existed for several centuries. One legend says that the lake monster scared to death the Tatar-Mongol army that headed for Novgorod in the 13th century. Batu Khan stopped the troops on the sides of Lake Brosno to rest. Horses were allowed to drink water from the lake. However, when the horses ventured down to the lake, a huge roaring creature emerged from the water and started devouring horses and soldiers. The Batu-khan troops were so terrified that they turned back, and Novgorod was saved. Old legends describe an “enormous mouth” devouring fishermen. Chronicles mention a “sand mountain” that appeared on the lake surface from time to time. According to another legend, some Varangians wanted to hide stolen treasure in the lake. When they approached the small island, a dragon came to the surface from the lake and swallowedthe island up.
It was rumored in the 18th and 19th centuries that the giant creature emerged on the lake surface in the evening, but immediately submerged when people approached. It is said that during World War II the beast swallowed up a German airplane. Today, there are lots of witnesses who say they chanced to see Brosnya walking in the water. Locals say that it turns boats upside-down and has to do with the disappearance of people.
This is taken from the absolutely-factual without-any-doubt account found on Wikipedia.