What is the significance of death what is the character described as?
Death, Satan's son, is literally conceived in Sin, as he is born of Satan's incestuous union with his daughter, Sin. True to his parentage, Death becomes the father of all sins, as he rapes his mother, Sin, almost at the moment of his birth. Guilty of rape and incest, he would also be guilty of matricide, but for the fact that Sin's demise would also be his own. As it is, he and Sin continue in an uneasy co-existence, characterized by hatred and pain. Death is described as a crowned but shapeless terror, before whom even Hell trembles, and who dares to threaten even Satan with his fatal dart.
It is also important to note that Milton's representation of death makes it very clear to us that death itself is the consequence of man's sin. God had planned for man to live forever in Paradise until it was corrupted by Satan, and sin entered into the world. Remember that Satan's first sin was disobedience, as was man's when he ate of the tree that God had forbidden, therefore humans are subject to the same ramifications that Satan and his fellow demons are: eternal damnation, but before that must come a physical death on the earth which is the bridge to the punishment for sin.