"In both upper corners are monster eyes, and a "bunch of grapes" signifying Cauac Monster can be seen near the left eye. Many tendril shapes are visible in the lower half of the relief, some with dots infixed, perhaps suggesting the forms of aquatic plants. So the original frieze may have been decorated with scenes of vertical human figures surrounded by Cauac Monsters and aquatic plants alternating with niches containing human figures seated on zoormorphic thrones. This scheme probably wrapped all around the four sides of the structure."
Carolyn E. Tate, Yaxchilan: The Design of a Maya Ceremonial City, p. 189-90