Answer:
Because of the color (turquoise blue), and the symbols that ornament the vessel, especially the eyes, and the mouth.
Explanation:
The color could represent water, and it's proximity to agriculture and terrain fertilization. When it comes to the look of this god, somehow it's a grotesque portray, but if we try to understand how the Aztec did, we can clearly see why Thaloc is portrayed this way. Rain plays an important role in that people's lives, and god such as this, who controls the water, is totally normal to see him as a monster who must be respected.
