User blog comment:RisingFusion/Beings vs. Monsters/@comment-25037895-20150603194014

Definitely the definitions shed some light on this subject.

Being
 * the nature or essence of a person
 * a real or imaginary living creature, especially an intelligent one

Monster
 * an imaginary creature that is typically large, ugly, and frightening.
 * a thing or animal that is excessively or dauntingly large