Here are the contexts of the quotes tweeted from October 9 through October 15, 2014. All but the last are from The Two Towers, by JRR Tolkien.

Map Rohan“Oft evil will shall evil mar.” Theoden, quoting a saying to Gandalf as they discuss the palantir.

“Perilous to us all are the devices of an art deeper than we possess ourselves.” Gandalf, discussing how the palantir may have led to Sauruman’s downfall.

Map Mordor“If it must be, let’s get it over.” Sam, when Frodo has decided to climb down the face of the Emyn Muil by rope.

“If we kill him, we must kill him outright.” Frodo, after they have captured Gollum.

“What he means to do is another matter.” Frodo, still considering what to do with Gollum.

“Now that I see him, I do pity him.” Frodo, replying to his memory of Gandalf’s words about Gollum, back in the Shire. (It was the Shire in the book, though the speech was moved to Moira in the movie.)

“Just try and stop me.” Sue Ann Bowling, Homecoming. Marna’s response to Lai’s suggestion that they take in Roi.