Stone Speaks to Stone (Greenwing & Dart, #1.5)

Jack Greenwing is good at scouting. He's renowned for being able to hold on in battle long past bravery. He was once given a trophy for his courage by the hand of the Emperor himself.

At Loe, where the Stone Speakers can call down avalanches and landslides, he was sent out on a scouting mission as a siege closed in on his company. He returns to see it being lifted because of treachery, and is there to witness the five remaining members of the command staff be led off in chains into the mount...