A rhombohedron is to a rhombus what a cube is to a square. A golden rhombohedra is composed of 6 golden rhombi each with a height and width in the golden ratio.
A bunch of people are obsessed with the golden ratio. As a single example, all segments of a pentagram are in the golden ratio with the next larger/smaller segment. There are many more examples on its wikipedia page.
And yes, a rhombic hexecontahedron is a 3-dimensional shape.
And... back to the topic:
The purpose of the spiky thing in Vindictus is simply as a placeholder object, for when the game tries to access a mesh that doesn't exist.
I had this glitch, where I would put on the bunny hat from the easter event on my Karok, and he would immediately sprout a perfectly white tail, he would be bald, and if I walked it would be in some weird humping motion.