This quest begins immediately after Glory Regained.
From Grantebridge, head directly west to an area northeast of Earnningstone. Here you will find Galinn waiting for you. You can reach the area easily be heading over the bridge located northwest of Grantebridge. When you reach Galinn and his small group of warriors, speak with him to learn of his plan. You will also have the opportunity to ask him some questions about why he joined Soma’s clan, and what he thinks of her inner circle. When you’re done talking, follow Galinn southwest to Earnningstone. Your task now is to burn and pillage the settlement, house by house.
As you raid through Earnningstone, throw lit torches on the rooftops of the buildings to set them on fire. Once the first few houses are burning, a number of enemies will attack. Most of these are regular warriors which aren’t difficult to deal with. The only more powerful foes that you will encounter are a Yeoman and a Pikeman. These have defences which are much tougher to penetrate, and will depend on exploiting parries / blocks to execute stun attacks, or spamming heavy attacks. If you’re having trouble with the timing, you can always use your special abilities to bring them down quickly, or shoot their weak points from afar. The Pikeman will drop a Wealth item in the form of a Carbon Ingot, so be sure to loot them when they’re dead.
When you’re done looting each house, focus on filling the ‘Pillaging progress’ bar in the top left of your screen, indicating how much remains to be set on fire before your objective is complete. When all the houses are burning and all the guards are dead, you can speak with Galinn to complete the quest.