These are the contexts of the quotes tweeted from @sueannbowling between August 21 and August 27, 2014.
“Who can swear certainly to anything of the Power?” Andre Norton, The Warding of Witch World. Frost, refusing to promise something she is uncertain of.
“No two Powers are alike—just as no world copies another to the last blade of grass.” Andre Norton, The Warding of Witch World. Frost, again saying she can not be sure how the Power will work.
“Always the Dark will rise—for it cannot be entirely driven from any world of man.” Andre Norton, The Warding of Witch World. Koris, at the last great conference after the Warders have returned.
“We must always strive to learn more and put what is so learned to proper use. Andre Norton, The Warding of Witch World. Koris again. And this sentiment, especially the second part, is very appropriate for today.
“He had a right to be alive, hadn’t he?” Andre Norton, Storm over Warlock. Shann Lantee, feeling as if he has been somehow blamed for being the only survivor of the Terran camp.
“There is no reason for us to advertise our being alive.” Andre Norton, Storm over Warlock. Ragnar Thorvald, pointing out that taking a Throg weapon, useful though it might be, would alert the aliens to possible survivors.
“That sort of thing just isn’t supposed to happen.” Sue Ann Bowling, Tourist Trap. Penny, speaking to Roi after his carelessness with the warnoff has brought on a puma attack.