The incident of the young master of Verzalys dying was not known to any of the houses. Llewel decided to keep it to themselves for the time being, he doesn't want the other houses to use this as an opportunity so that they can do their sinister plan. Even his return from the dragon lands was concealed and the warriors who were supposed to return with him, returned to the dragon lands to give the other houses the illusion that he was still there.
They kept this up until they had gathered enough information and list of people who were behind his son's death. Preparations were made for a large-scale attack. They were well aware that they will be facing the four houses but none of them cares. After exposing the sinister plan against them, they did not feel anymore remorse. They won't sit around waiting for their deaths, they will fight for their life.