Hyeonmu(black tortoise and serpent) symbolizes seven of the 28 constellations, situated
in the northern portion of the star chart. The belief of the Five Elements soon gave rise to the
worship of the so-called ‘four cardinal deities’, making hyeonmu the guardian deity of the
underworld.
In Goguryeo tomb murals, hyeonmu was depicted as a serpent coiling around a tortoise.
Initially, it bore a rather awkward appearance, with the heads of serpent and tortoise were depicted as
that of the beasts. Later on, as its importance within the visual language of tomb murals grew,
hyeonmu gradually shed its rather primitive appearance. Hyeonmu was afforded more refined
and elaborate details, eventually acquiring its characteristically esoteric look. From the 6th century
onwards, the representations of hyeonmu became highly sophisticated, brilliantly colored and
conveyed vigor and liveliness,  eloquently showcasing the consummate artistry of Goguryeo
painters.