The fanged skull that the curse had adorned Kei with was not of a cat, nor human.
Ophelia had chosen it in specific.
The skull carried characteristics of both, rather.
There were reasons behind every aspect of his curse.
Lynx comes from the Indo-European root *Leuk- 'Light, brightness'.
Lynx is the name of a constellation in the northern sky, defined by Johannes Helvetiusin 1687. The name is said to have been chosen because the stars which make up the constellation are so dark that only those with the eyesight of the lynx can perceive them.
The Lynx is a cat that originates in North America and Europe.
Ophelia had left her home in Europe at a young age,
to pursue her career in opera in the Americas.
Secondly, the Lynx is a solitary creature. It is smaller in size, more so similar to a domestic cat rather than the larger breeds. They are known to leave their mother's care at young ages and are solitary creatures. They spend their lives alone, hunting at night under the cover of darkness.
It is said that the Lynx's eyes can look through anything, in fact, their name comes from the luminescence of their eyes. The species has been accredited with being able to look straight through material objects as if they were translucent.
"... the acuity of the lynx arose from two paired and complementary virtues - sharpness of vision and depth of insight, the outside and the inside, the eye and the mind""just as the lynx, with its superior vision, not only sees what lies outside but also notes what arises from inside"