D&D: Storm King's Thunder - Silence at the Table

A couple of weeks ago we had our regular Friday night D&D session with a new player coming to the table. Our group is still playing through Storm King's Thunder (nearly 3 years now), running around the countryside in chapter 3. They are in a home-brew session at this point, on assignment from the Harpers. 

Our party was working their way up to Termalaine looking for four other Harper agents. When they arrived in the city they found it to be eerily quiet, with the gates swung wide open. Our monk shadow stepped his way into the city to investigate and found a city that was in ruins from a recent attack by a war party. 

The usual D&D banter and roleplaying ensued from there with several of the NPC's. What happened next though caught everyone at the table by surprise, including myself.