In Greek/Roman Mythology:
In ancient Roman religion and myth, Saturn was a major god presiding over agriculture and the harvest time. His reign was depicted as a Golden Age of abundance and peace by many Roman authors. In medieval times he was known as the Roman god of agriculture, justice and strength. He held a sickle in his left hand and a bundle of wheat in his right. His mother was Terra and his father was Caelus. He was identified in classical antiquity with the Greek deity Cronus, and the mythologies of the two gods are commonly mixed.
Saturn’s wife was Ops (the Roman equivalent of Rhea) and Saturn was the father of Ceres, Jupiter, Veritas, Pluto, Neptune, and Juno, among others. Saturn had a temple on the Forum Romanum which contained the Royal Treasury. Saturn is the namesake of both Saturn, the planet, and Saturday (dies Saturni).
Saturn is often identified with the Greek Cronus. In Hesiod's Theogony, a mythological account of the creation of the universe and Zeus’ rise to power, Cronus is mentioned as the son of Uranus (the Greek equivalent of Roman Caelus), the heavens, and Gaia (the Greek equivalent of Terra), the earth. Hesiod is an early Greek poet and rhapsode, who presumably lived around 700 BC. He writes that Cronus seizes power, castrating and overthrowing his father Uranus. However, it was foretold that one day a mighty son of Cronus would in turn overthrow him, and Cronus devoured all of his children when they were born to prevent this. Cronus’s wife, Rhea (often identified with the Roman goddess Ops), hid her sixth child, Zeus, on the island of Crete, and offered Cronus a large stone wrapped in swaddling clothes in his place; Cronus promptly devoured it. Zeus later overthrew Cronus and the other Titans, becoming the new supreme ruler of the cosmos. (taken from Wikipedia)
In Sailor Moon:
Sailor Saturn, aka Hotaru Tomoe, and the last addition to the Outer Senshi. Sailor Saturn has frightening destructive powers on a planetary scale, but can also heal minor injuries and put up energy barriers. Hotaru was a kind but lonely girl with no friends until Chibiusa came along. She had a very weak body and suffered from countless seizures because an alien entity, Mistress 9, had been implanted inside of her body. As if that weren’t enough, Hotaru was also the reincarnation of Sailor Saturn, the most feared Sailor Senshi, whose awakening brought about destruction and silence. After a very long and arduous battle, where Saturn ended up losing her life, she was reborn into a normal baby to be raised by the Outers (in the manga and Stars season) or her father (in the anime). She later grows up to be a much happier girl and now works alongside the Senshi instead of being feared by them.
First and foremost, I want to point out that a common misconception in the fanbase is that Takeuchi mixed up the powers of Sailors Pluto and Saturn, as Saturn was considered a god of time and Pluto was the god of death. However, its clear that this was intentional on Takeuchi’s part and she actually did much research. You can read a wonderful article on this by Genvid. I highly recommend it!
Sailor Saturn’s Silence Glaive is a scythe-like object obviously referencing the scythe Saturn uses.
The history of Saturn is double in nature. The original Saturn was the Italian god of agriculture and prosperity. The Romans later identified him with Cronos, the oppressive Greek god of time and gloom. The Romans were conscious of Saturn’s dual nature. In fact, two English adjectives derived from Saturn, Saturnian and Saturnine, are direct opposites: the former meaning happy and prosperous, the latter meaning gloomy and sullen. Duality reflected, possibly by coincidence, in the happy child Hotaru, and the cold, gloomy Messiah (Sovereign) of Silence. (Taken from Tripod)