If instructed to learn, you may do nothing. Discarding a card and putting a Lesson card into your hand are both optional.

If you bring a card into the game from outside the game in a Sealed Deck or Booster Draft event, you may select only a card that is in the card pool that you built your deck from.

If you bring a card into the game from outside the game in a Constructed tournament (or a Constructed game played under tournament conditions), you may select only a card from your sideboard. In casual Constructed games, the card comes from your collection.

If a card is brought into the game from outside the game, it will stay in the game until it ends or until its owner leaves the game, whichever comes first.