His Eye was a representation of his malice and hatred. The Eye of Sauron seems to be a mental weapon. Enemies of Sauron regularly describe the Eye constantly seeking to invade their minds.

The Eye of Sauron is a mental weapon that constantly invades enemies' minds, causing fear and horror. Gandalf battles the Eye of Mordor, but he remains capable. Frodo and Galadriel feel the Eye ...