These cards all have to do with modifying and using the discard pile. It turns out that "Winter is Coming!" is a particularly useful card that inspired a whole bunch of things to do with all the extra cards in the discard pile. Things like "Grave Robber", "Night of the Living Dead", and "The Necromancer" are all examples of the kinds of things that can be done with a huge discard pile.
Cards like "Brothers of the Nights Watch" can stem the tide, and also add a bit of theme to complement "Winter is Coming!".