‘… where there is light there is shadow, friend. Something is stalking our city, wreaking destruction and then disappearing without a trace … we have to fight – join us, the Second Salemers, in our fight … hear my words and heed my warning … and laugh if you dare: WITCHES LIVE AMONG US!
-- Mary Lou Barebone (Part 1)

Importance: The first part of this quote references the invisible, deadly force that stalks the city and eventually plays a key role in both the story's climax and in a pair of deaths that lead to that climax. The second part of the quote develops the idea that the wizarding community in America is feared and watched for, suggesting that Madam Picquery and others (including Percival Graves) are correct: No-Maj's like Mary Lou Barebone and the church with which she is involved are a threat.

I’m more of a chaser, really.
-- Newt Scamander (Part 1)

Importance: This quote is something of a pun with a double...