Who was the destroyer of the first born of Egypt?

Exo 12:23  For the LORD will pass through to smite the Egyptians; and when he seeth the blood upon the lintel, and on the two side posts, the LORD will pass over the door, and will not suffer the destroyer to come in unto your houses to smite you. 

Many believe that it was God who killed them all. If God will not suffer the Destroyer to come into the Israelite houses does this mean He is restraining Himself? Does that make sense? If Christ destroyed the first born in Egypt does that mean those who are crucified with Christ and who believe that Christ is in them have a destroyer abiding in them?

For the Son of man is not come to destroy men's lives, but to save them. Luke 9:56

The evidence shows clearly that Satan is the Destroyer and it is God who restrains him from doing His evil work.

Thus the archfiend clothes with his own attributes the Creator and Benefactor of mankind. Cruelty is satanic. God is love; and all that He created was pure, holy, and lovely, until sin was brought in by the first great rebel. Satan himself is the enemy who tempts man to sin, and then destroys him if he can; and when he has made sure of his victim, then he exults in the ruin he has wrought. If permitted, he would sweep the entire race into his net. Were it not for the interposition of divine power, not one son or daughter of Adam would escape.  {GC 534.2}