I possessed another player. His hand has a Possession--which I don't play, to avoid him Posessing me. I play all the other cards in his hand except the Possession, with Sword (treasure) last. Sword requires that "each other player discards down to 4 in hand". Since I am playing the "other player" under my possession, he no longer has enough cards for me to discard him down to 4. He only has the unplayed Possession in his hand. So the game is in a impasse. I can't discard the "other player" down to 4, and nobody can proceed. See attached screen grab.