In this scene, we learn that the "Covenant's poison" is similar to the poison that Yu's lover, the Ming, used to poison his wife. The Ming tells the Emperor that he's disappointed in the way that he treated his wife, and that he wishes he could have let her go. The Emperor tells the Ming to kill the Ming with this poison and he'll give the Ming back.
In this scene, we learn that the "Covenant's poison" is similar to the poison that Yu's lover, the Ming, used to poison his wife. The Ming tells the Emperor that he's disappointed in the way that he treated his wife, and that he wishes he could have let her go. The Emperor tells the Ming to kill the Ming with this poison and he'll give the Ming back.