EDIT: Now how in the blazes did I manage to get this into the wrong forum? Sigh. Creating a new thread in the rules forum. Ignore this one. The right one is here .

Okay, Threat from the East states that:

When revealed, you choose one:

• Each player draws 3 cards and then discard 3 random cards from hand.
• Each player discards 3 random cards from hand and then draws 3 cards.

Now, how does the latter choice interact with Knight of Harrenhal:

If a card would be discarded from your hand at random, you may choose the card to be discarded instead.

Mainly, if we go with the second option (discard 3 at random ), and a player decides to use Knight of Harrenhal's ability (note the word may, so it's not obligatory) to choose the cards that he/she discards, then does the then portion of Threat From The East interpret the first portion as not having completely resolved succesfully or not? I.e. how does the replacement effect (replacing random with choice ) in Knight of Harrenhal interact with the fact that Threat from the East requires all players to have discarded 3 cards at random, for the second portion of drawing 3 cards to happen?

Here's Ktom's answer from the rules forums:

Correct. The replacement effect - making the discarded cards intentional instead of random - still counts as a successful discard of "random" cards. The important thing to remember is that even though the Knight lets you choose the cards, it is still the plot that discards them from your hand.

That's all "success" is measured on - did the plot make 3 cards leave your hand. If "random" was a strict measure of success, then would the plot succeed in discarding 3 random cards from your hand when you have exactly 3 cards in your hand?