The bagua mirror is among the most well known and commonly used of all the Feng Shui protection spells, remedies, or magical cures for improper placements of houses. Buildings placed near graveyards, bridges, railroads, or overpasses, or those located at a T-junction or with a large tree blocking the entrance are said to be at a disadvantage from poison arrows or Shar Qi that damage those inside the dwelling or place of business.

To protect against and counteract bad luck caused by arrows of Shar, Feng Shui practitioners invoke the eight trigrams or bagua of the Early Heaven. The use of these mirrors is said to date back to the 10th century, but the bagua itself is far older than that, for it consists of the same eight Trigrams found in the I Ching or Chinese Book of Changes used in divination, which is said to have originated more than 200 years B.C!