Plagues: The plagues in Egypt had more meaning than the obvious. Life is in the blood, so this first plague confronts life itself and portends the tenth plague.

Pharaoh is told before any Plague is sent that the Firstborn will die unless Pharaoh cooperates:

Exodus 4:22. And you tell Pharaoh, ‘Thus says the LORD*, Israel is My son, My firstborn. 23. And I say to you, Send My son away! So he can serve Me, and if you refuse to send him out, behold, I AM will slay your son, your firstborn.”