What does "against" mean?

“Give me the boy, Your Grace. It is the surer way. The better way. Give me the boy and I shall wake the stone dragon.”
“I have told you, no.”
“He is only one baseborn boy, against all the boys of Westeros, and all the girls as well. Against all the children that might ever be born, in all the kingdoms of the world.”
“The boy is innocent.” (Game of Thrones)

Context: Melisandre asked King Stannis for a bastard son of his brother as a sacrifice to the God for the king's great cause: they were to fight a supernatural force which were about to attack and sweep through the kingdom. If the supernatural force should prevail, mankind will be eradicated.

Hi, dear teachers. Does the “against” mean “compared with” here?
Thank you.