Ser Barristan Selmy says that after he comes into play, all players shuffle their discard piles into their decks. He was played in round 1 when only 1 player had a discard pile. Are you supposed to shuffle your empty discard pile into your deck (essentially just shuffling your deck) or if your discard pile is empty do you just not shuffle anything? If this has already been ruled on I apologize, however, I was not able to find anything so any input would be appreciated. Thanks.

If your discard pile is empty, there is nothing to shuffle "into" your deck. So the effect fails for that player and they do nothing.

Thank you, that was how we played it, appreciate the confirmation.