On the Mirage Flats southeast of Hay Springs, Alkali Lake—later known as Walgren Lake—spawned Nebraska’s strangest lake-monster legend. Early tales and 1920s newspaper stories turned the lake into the home of Giganticus Brutervious, a beast described in wildly vivid terms: a roaring sea reptile, a giant catfish, a monstrous mudpuppy, even a horned alligator-like brute that could come ashore for livestock and waterfowl. The most memorable version gave it flashing green eyes that spat fire, pointed ears, a tail powerful enough to whip the lake into a storm, and a head “like a huge oil barrel” shining black in the moonlight. The legend was helped into print by the tall-tale machinery around John G. Maher, but it dug in deeper when Mari Sandoz echoed the monster in Old Jules, giving the creature a life beyond a single newspaper hoax. Even after eyewitness reports thinned, the lake itself kept the story breathing; the water remained the hotspot, and the monster never really detached from that lonely Nebraska basin.