Characterization: Abigail Williams drinks the blood in an attempt to kill John Proctor's wife. This shows pretty early that she wants to get John's wife out of the way so that she could be with him
Dramatic Irony: We know that John had confessed to committing adultery but his wife did not. So she lies to the court saying he did not cheat in an attempt to protect him when in reality it was doing the opposite.
Theme: One of the themes in the Crucible is that Hysteria can tear a community apart but, some people thrive on hysteria as well. A great example of this is how hysteria and the fear of witches lead the people of Salem to sentencing their people to be hanged with out any real evidence.
Characterization: John Proctor doesn't believe that there are witches in Salem from the beginning because he thinks that there is probably a much more reasonable explanation. This shows that John is more level headed than most of the people in Salem because he isn't just falling into the hysteria.
Dramatic Irony: Another example of dramatic irony in The Crucible is how we know that Abigail or any of the other girls actually see witches/spirits during these trials but most of the people believe that they are seeing these spirits
I SEE DEAD PEOPLE
Theme: This scene shows that some people will thrive off of hysteria. Abigail Williams and the other girls will continue to pretend to see things just because they received a large amount of power from it