At this moment Satan is shown as weak and ready to give up. His long journey to the Garden of Eden has given him time to think and he is considering his options. This represents one of Satan's weakest moments where he is shown as weak and indecisive. He realizes that there is no way to defeat God and that his rebellion was a failure. This phrase is formed as a command in which Satan is doing the commanding. I think he wishes that he could command God to relent on his punishment. Satan realizes that he has made a mistake and an eternity of torture awaits him unless God relents his sentence. The exclamation point makes the sentence jump out. It makes Satan sound exasperated and seem as though he is crying out for God to forgive him. 

These lines also echo Claudius' attempt at repentance in Hamlet 3.3.40. Also, "place for repentance" is similar to the language of Hebrew 12:17 dealing with Esau's sale of his birthright in Genesis 25:24-31.