According to old folks, eclipses of the moon or sun were caused by the Bakunawa (literally, large looped serpent). This mythical sky-serpent—which is also associated with darkness that comes with the New Moon—of Asian folklore has analogues in China, India, Malaysia, Mongolia, and Thailan but, nowadays, is in the Philippines where the legend most persists.
Among Southeast Asia folklore, this sky-serpent is often associated with the Naga King Cobra, a deity of serpentine features able to control some weather aspects. As a celestial Naga, the Bakunawa was responsible for rains, wind and eclipses. Usually depicted as a snake with a looped tail, the Bakunawa was said to inhabit either the sky, the underworld, or the depths of the ocean. Because in the Hindu tradition eclipses were caused by "a serpent devouring the sun and moon" as the myth of the Bakunawa became part of Philippine folklore, this beast soon became known as the "Devourer of Moons" or "Moon Eater."
Later account within Philippine folklore, describe the Bakunawa as dragon or serpent with added part of many other animals so that it head resembles a shark with gills and a lake-sized mouth with a striking red tongue. Around the mouth, whiskers one palm (20 cm) long let the beast sense the air. Two powerful ash-gray wings allow the beast to move across the sky, while smaller wings along its sides allow it to stay suspended in one position as it devours the sun or moon during an eclipse.
Legend has it that long ago there were seven moons in the sky, but hungry, the Bakunawa gobbled them up one by one until it came to the last and largest moon. The moon was so large, and the beast so full, it failed to swallow it, so it started to bite it, sinking its teeth deep into the moon’s surface. But the moon was too hard, and soon the beast abandoned its endeavor. However, to this day, the Bakunawa’s teeth-marks can be seen on the moon.
Every now and then, the Bakunawa will take to the sky and attempt to finish the job it started by swallowing the moon—or the sun if it’s hungry enough—causing an eclipse. Accustomed to the silence of the sky, the beast is skittish, and to make it release the moon or sun, people should go on the streets loudly clanging utensils together to startle it. A tradition described as "weird lamentations" after two Spanish missionaries witnessed an eclipse, in the 17th Century, and described how during the eclipse Filipinos of various districts "generally go out into the street or into the open fields, with bells, etc., and by making a noise with these objects, attempt to liberate the moon" from the dragon.
In this later tradition, the Bakunawa’s den is always in the deepest parts of the ocean. And despite his massive bulk doesn't remain immobile, but is believed to shift his direction in four sudden 90 degrees movements every calendar year: In spring (January, February, and March) its head faces north and its tail south. In the summer (April, May, and June) it turns to face west while its tail points to the east. In autumn (July, August, and September) its head points south and its tail north, and in winter (October, November, and December) its head is east and its tail west.
Because the Bakunawa (particulary when envisioned as a Celestial Naga) is thought to broadcast evil and misfortune from its mouth, in many Southeast Asian cultures, the invisible rotation of the Bakunawa provided Visayan house-builders with means to divine the best time to build houses, as it was vitally important to orient the metaphysical aspect of one's movements to avoid the current direction of the Bakunawa's venomous broadcast. So, "the position of the dragon at any given time" provided builders with time and space coordinates for positioning house posts, staircases, and doors.
-Mojares, R.B., 1999. Dakbayan: A cultural history of space in a Visayan City. Philippine quarterly of culture and society, 27(3/4), pp.117-132
-McCoy, A.W., 1982. Baylan: animist religion and Philippine peasant ideology. Philippine Quarterly of Culture and Society, 10(3), pp.141-194.
-Ramos, M.D., 1967. The Creatures of Midnight: Faded Deities of Luzon, the Visayas and Mindanao. Philippines, Island Publishers.