Mythology

Mythology is a collection of myths, especially one belonging to a particular religious or cultural tradition of a group of people – their collection of stories they tell to explain nature, history, and customs – or the study of such myths. 
Percy Jackson and the Olympians, The Kane Chronicles, The Heroes of Olympus, Magnus Chase and the Gods of Asgard, and The Trials of Apollo all center on the presence of various mythological concepts in the modern world and the forces put in place to combat them. A recurrent theme is the emergence of a malevolent figure from mythology seeking to destroy the world, only to be defeated by modern-day heroes with the aid of their gods.
The following mythologies have appeared in Rick Riordan's works with starring roles in various series. As well as playing a role in most of the books published under the Rick Riordan Presents imprint. 
== Greek mythology ==
Greek mythology is the collection of myths belonging to the ancient Greeks, especially based on accounts written by well-known poets or philosophers such as Homer, Hesiod, and Plato. It revolves mostly around stories concerning the Ancient Greek pantheon and the mortal heroes such as Odysseus and Achilles.
It is prominently featured in Percy Jackson and the Olympians and The Heroes of Olympus, focusing largely on the Second Titan War and Second Giant War fought by the demigods of Camp Half-Blood and Camp Jupiter.
The Greek gods are strongly tied to a metaphysical force known as Western Civilization, residing wherever the "flame" is brightest. The current epi-center of Western Civilization is the United States of America, specifically New York City.
== Egyptian mythology ==
Egyptian mythology is the collection of myths from Ancient Egypt. It is prominently featured in The Kane Chronicles trilogy, focusing largely on the War Against Apophis and his forces of chaos by the magicians of the House of Life. Many of the Egyptian gods were banished to the Duat when Egypt became a part of the Roman Empire.
Thousands of years later, they were released by Julius Kane into the modern world. Unlike most pantheons shown, they do not have offspring with mortals, rather then have a form of symbiotic relationship with magicians who share a magical affiliation with their attributes and, in rare cases, demigods from other pantheons.
== Roman mythology ==
Roman mythology is the collection of myths belonging to the ancient Romans, especially based on the accounts of esteemed Roman poets such as Ovid and Virgil, whose greatest works include The Metamorphoses, a poem describing changed forms and bodies, and the birth and growth of the world, and The Aeneid, a poem describing the travels of Aeneas after the fall of Troy, and his subsequent founding of Rome.
It is prominently featured in The Heroes of Olympus series. When the flame of Western Civilization shifted from Greece to Rome, many of the Greek myths were reinterpreted under Roman names, thus causing the gods to develop alternate forms and forming the basis of Roman mythology.
== Norse mythology ==
Norse mythology is the collection of myths belonging to the Germanic and Norwegian people. It is prominently featured in Magnus Chase and the Gods of Asgard, focusing largely on the Einherji of Hotel Valhalla preparing for Ragnarök.
The Norse deities are divided into three aspects, the aesir, gods of war and power, the vanir, gods of peace and magic, and the Jotunn, a race of semi immortal giants. All three are capable of siring demigod children with humans, dwarves, and elves.
The Nine Worlds of the Norse myths are each home to a different group of beings. Asgard is home to the Aesir gods, Midgard is home to humans, Vanaheim is home to the vanir gods, Muspellheim is home to the fire Jotunns, Niflheim is the land of cold, Helheim is home to the dishonorable dead, Alfheim is home to the elves, Nidavellir is home to the dwarves, and Jotunheim is home to the Jotunns.
== Trivia ==
* Rick Riordan has mentioned in a interview that he is finished with Greek Mythology and Roman Mythology because he cannot find any antagonists, opposing forces, or entities from or in Greek Mythology and Roman Mythology for his books.
* Percy Jackson's Greek Gods and Percy Jackson's Greek Heroes are retellings of several Greek myths.
* Aside from the above myths that have gotten a series focused on them, several other mythologies have been hinted or confirmed to exist in the main series and Rick Riordan Presents:
** God is mentioned by Chiron in The Lightning Thief and Leo Valdez in The House of Hades.
** Thor mentions wanting to fight Jesus Christ in The Sword of Summer.
** Moses is the only foreign magician to have defeated the House of Life in a duel.
** Throughout The Heroes of Olympus, Piper McLean recounts Cherokee myths. Similarly, Frank Zhang and his grandmother believe in Chinese myths and gods.
** Apollo mentions a Chinese celestial dragon in The Dark Prophecy.
** Mallory mentions Irish Celtic myths in The Ship of the Dead, while Dagda is referenced in Aru Shah and the End of Time. Lugus and the Celtic Gods are referenced by Apollo in The Tower of Nero.
** Mithras and the Leontocephaline are Roman-Persian deities with origins from Persian mythology.
** Apollo in the Burning Maze referenced Mefitis, a god of the Samnite People of south central Italy.
** A Thai Goddess of the Household, Nang Kwak, is mentioned in The Tyrant's Tomb. 
** Avalon, an island crucial to the Arthurian Mythos, was mentioned in Aru Shah and the Song of Death as a destination.
* It was mentioned in Percy Jackson's Greek Gods that every mythology had some story about a flood similar to the story of Noah's ark in the Book of Genesis.
** In Greek Mythology, Zeus was the one who sent the flood and the two survivors, Deucalion and Pyrrha, who were warned by Prometheus, hid in a chest to survive. This is actually just one myth of three, the other two involved Ogyges and Dardanus.
** In Egyptian Mythology, when Ra sent Sekhmet to destroy humanity for not worshipping him, it caused a flood of blood.
** In Norse Mythology, a flood of blood from Ymir appeared after he was killed by Odin and his brothers and it eventually became Earth's ocean. The flood drowned most of the Jötunn, but one named Bergelmir and his wife managed to escape on a lúðr and found a new race of ice giants in the mountains.
** In Hindu mythology, Matsya, the first incarnation of Vishnu, warned a man named Manu about an upcoming flood.
** In Maya Mythology, Hurakan and K'ukumatz sent a flood to destroy the mud people they created due to them being weak and useless.
** In Mesopotamian Mythology, Enlil, the god of wind, earth, and storms brings the flood but Enki warns Atrahasis to take apart his house and build a boat. Atrahasis stayed with his family and animals for a week.