In Egyptian mythology, Ra fights a giant serpent every night

Explanation

Each night his solar barque travels through the Duat (the underworld), where the serpent Apophis, embodiment of chaos, tries to stop it. Priests performed daily rituals to help Ra win. Fun fact: the asteroid 99942 Apophis, which will pass closer to Earth than some geostationary satellites in 2029, is named after this serpent.