Menō

Menō was described as "a massive lizard with a bipedal walk, thick leather skin covered with horns, cone-shaped fangs, and sharp claws." His standing height was 80 centimetres, but the actual length of his body is over two meters from head to tail. Zansūru identified Menō as a "Tirano" (肉食獣, ティラノ, literally meaning: Carnivore), presumably a reference to Tyrannosaurus. The manga and anime depicted him as resembling a Velociraptor, with a blue stripe running along his sides.

Menō was a dinosaur that lived in the Land of Redaku millions of years ago. He died while he was still a juvenile. After his death, the wetlands common throughout Redaku preserved his remains, eventually becoming fossils. Over the following millennia, the wetlands changed into a vast mountain range, at the peaks of which dinosaur fossils could commonly be found. It was here that Menō's fossils would eventually be dug up, not far from the Astronomy Research Institute. A few years prior to the events of Sasuke Retsuden, Zansūru, a paleontologist, discovered a way to revive the dead. He came up with the idea of reviving dozens of dinosaurs to be used as an immortal army in the service of Redaku's Prime Minister, a plan he recruited Jiji to help him with. To test the technique, they revived one dinosaur, which they named "Menō". Zansūru was happy with the result, but did not want to revive additional dinosaurs until a sufficient number of fossils could be assembled. Until then, Menō was charged with guarding the Institute, keeping the prisoners incarcerated there in line. Being immortal, Menō did not need to eat or sleep, enabling him to patrol the Institute all day, every day. He was given instructions to execute any prisoners who tried to escape, publicly and as gruesomely as possible, in order to discourage additional escape attempts. In this task, Menō was incredibly effective, as not even messenger hawks could come and go from the Institute without permission; this permission was represented by a red cloth, ordinarily only in the possession of the Institute's staff. Over time, Menō's efficiency caused the prison guards to become lax in their duties, to the point that they stopped locking prisoners' cells at night, instead depending on fear of Menō to keep the prisoners obedient. Despite his constant patrols, Menō did occasionally have some time to relax, which he often spent curled beneath an almond tree; Jiji theorised that he liked the smell.