Primary
Travel along the path, mostly south, killing undead until you reach the outpost.

Tip: Just before reaching the outpost, you will be blocked by a closed gate and a small patrol (the gate will open once the patrol is defeated). Unfortunately, several White Mantle have apparently died protecting the gate, providing ample minion fodder for the lone Zombie Warlock. However, he cannot support them for long and if you wait just a few minutes, the mass of minions will expire due to natural degeneration.

After speaking to Justiciar Toriimo (A on the map), continue through the gate and south along the beaches or across the bridge . Talk to Justiciar Hablion (B on the map). Help Hablion clear the swamps of the undead and kill the boss at location C on the map.

It can be quite hard to clear the swamps, even with the extra soldiers provided, since you tend to get overrun, and even player-controlled characters often stand in the poison water needlessly! If you get into trouble, run back to the soldiers standing above the swamp and they will help kill for you.

Note: Do not make the mistake of following Justiciar Hablion for the entire mission. He takes a different path than that of the main mission, and you will waste a significant amount of time if you follow him instead of his forces (it is very clear when they split paths).

Note: It is not actually necessary to speak to Justiciar Hablion at all. Simply clearing all the Undead out of the swamp will trigger the end-of-mission cutscene. Note that if Hablion dies, the mission fails!

Bonus
To get this bonus, you have to talk to a pig (Oink) who is found to the left behind the gate at the very beginning of the mission (1 on the map). Return him to his owner in the village: the little boy Cheswick, son of Orrian Historian McClain (2 on the map). When approaching them, do not talk to either, as this has broken the bonus on at least one occasion. Instead, wait for the conversation between them to finish; the son will then say, "thank you for returning Oink," and the bonus objective will be added to your quest log.

Collect the tome from a chest in the water at the north end of the fjord (3 on the map) even though the father will tell you it is in a cove to the southwest, and return it to the historian in the village. Be careful, as opening the chest will trigger some quite high level Smoke Phantoms (3 at a time). You will also be ambushed twice more in the fjord while returning the tome to the historian.

Tip: The easiest way to get past the Smoke Phantoms is to have the whole party retreat to the beach after clearing the way to the chest, and have someone with a run skill fetch the text. He can simply outrun the phantoms without being hit more than a couple of times.

Tip:If you fight the Smoke Phantoms, make sure that the one who's going to pick up the tome knows to drop it immediately. This ensures that the whole party is ready to fight. The Phantoms' most deadly spell is Chain Lightning, but it loses effectiveness if it only hits one target. Therefore, do your best to spread out to minimize the damage (this is especially relevant to "soft" targets). Use AoE interrupting skills, such as Maelstrom and Meteor Shower, as soon as the phantoms spawn. These skills are effective at shutting down the phantoms and make the fights much easier. Additionally, try other caster shutdown skills, such as Power Block and Broadhead Arrow.

Tip: A very cheap way to complete the bonus is to grab the text and then kill a Mergoyle or other nearby enemy on the cliffs above the water. Now use Necrotic Traversal or Consume Corpse. You will be teleported up and out, thereby avoiding the Smoke Phantoms altogether, and it is an easy run back to McClain.

Tip: You don't actually have to return Oink to Cheswick to start the bonus. It may help to take him along with you and help tank the Smoke Phantoms. Bring him back along with the book and finish both objectives at once.