Proceed to the Charred Firewood at (I-7) and trade the Flint Stone to it.
The Charred Firewood is actually immediately north of the (I-7) tower but two levels above (on the same level as the Beaucedine Glacier (S)Campaign Arbiter). If you are at the Charred Firewood and facing south, you will see the (I-7) tower immediately below you. Be forewarned - you will have to pass 2 true sight Dryptotaur to get to the Charred Firewood.
Go to the Southern tower at (H-10) and click the Compressed Snow for a cutscene.
An immense beastman force seeks to strike at the sparsely manned rearguard of the northbound Allied expedition. You have been requested to join the Carmine Swallows on their mission to intercept the encroaching enemy host at Beaucedine.
SPOILER WARNING: Click here for additional details about this story line.