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.