Nature of the Beast

Nature of the Beast is one of the four main quest lines in Dragon Age: Origins that must be completed before calling the Landsmeet.

Background
The Dalish elves are being destroyed by a virulent disease which is turning them all into werewolves. The clan keeper, Zathrian, asks for your assistance in ridding them of the curse. He requests that you find the first werewolf, Witherfang, and return with his heart to end the curse destroying his people. The quest takes you through the Brecilian Forest to track down the lead werewolf.

The forest
After exploring the Brecilian Outskirts, travel to West Brecilian Forest. After fighting many werewolves, you will reach a waterfall with three paths and three werewolves, led by Swiftrunner, standing within it. A conversation will automatically occur when you approach them; with a high Coercion skill you can avoid combat. Regardless, continue into the woods after your meeting. In the next area, a hunter lies Wounded in the Forest; you may return him to the Dalish Camp or kill him.

Head to East Brecilian Forest for further encounters with werewolves and some sylvans. A side path offers the opportunity to complete Lost to the Curse, if you have spoken to Athras earlier. Eventually, you will arrive at an impassable barrie(southern most East Brecilian Forest); to remove it, find the Grand Oak (in the western forest) and the Mad Hermit (in the east).

Near the Grand Oak is a campsite; save before approaching it. Examining the campsite items (tent, sleeping bags, fire) leads to your party falling asleep. You can affect which party members are available during the battle by choosing dialogue options carefully. The surest path to survival involves avoiding examination any of the items: choose options which describe the setup as odd or dangerous and then attempt to leave; the party will be brought back to the campsite for a final dialogue option before the Shade attacks. When your character throws their hands up in the air, you will be battling with your entire group. If there is a momentary black screen, you only have one party member awake who has to attempt to defeat the Shade on their own (unless they're a Spirit Healer who knows Revival – then the fight can become ridiculously easy).

Forest barrier
To cross the barrier in East Brecilian Forest, you must help the Grand Oak retrieve his acorn or allow the Hermit to keep it by killing the Oak. If you choose retrieval, you can kill the Hermit or trade with him. He will accept one of four items in exchange:
 * The Tale of Iloren, a book received during Cammen's Lament
 * Dusk Ring from the campsite encounter in West Brecilian Forest
 * The scarf received during Lost to the Curse
 * Athras's Pendant, the reward from Lost to the Curse
 * Deygan's Boots, a possible reward from Wounded in the Forest (if you have looted him and don't have them equipped)

After passing through the barrier, the party will meet up again with Swiftrunner resulting in combat regardless of which dialogue options are chosen. After the battle, Witherfang appears and the rest of the werewolves scatter. You can now enter the Ruined Temple. This is a good time to clear out inventory; players have reported requiring over 100 empty inventory slots to pick up every item.

The ruins
Continue through to the Lower Ruins until you reach the main lair. Along the way, you will find one of the items for The Mage's Treasure, one of The Black Vials, and the Phylactery for unlocking the Arcane Warrior specialization.

The lair of the werewolves
The main lair is populated by Shadow Werewolves that are tougher than the ordinary ones. The first one is in a room littered with traps; disable them if possible. Eventually, you will reach the Lady of the Forest and have an opportunity to parlay, offering additional choices to complete this quest. You can also choose to avoid further discussion and fight her party.

Alternatively, a stealthy Rogue can sneak past the shadows to reach the main lair; after the curse has been ended, these foes will disappear.

The Warden's choices
During discussion, the Lady of the Forest will tell you that the problems began with Zathrian, who cursed the human settlers who had murdered his son and raped his daughter. The current werewolves are not those who committed these crimes, but the unfortunates who wandered into the forest since. The Lady of the Forest asks that the Warden bring Zathrian to the chamber so they may talk. Ultimately, you must choose to side with the Elves or the Werewolves. Most of your companions have strong opinions about this decision and it has consequences for the final battle against the darkspawn; choose carefully.

Kill the elves
With a high persuasion, the Lady of the Forest can be convinced that the best course of action is to kill all the elves. Killing the elves and siding with the werewolves results in negative approval from many of the companions including those who may not yet have been recruited. This results in approval from Morrigan and Shale, while Wynne, Alistair, Leliana and Zevran disapprove. With the elves dead the werewolves will agree to fight for the Warden and march with them against the darkspawn. All other resolutions result in the elves fighting for the Warden.

Kill the werewolves
If the Warden agrees to bring Zathrian before the Lady of the Forest he will be encountered as the Warden exits the ruins. Once Zathrian is brought to the Lady of the Forest the Warden can choose to engage the werewolves with Zathrian's help, who will tank Witherfang for much of the fight but will frequently freeze the party with Cone of Cold without careful positioning. After the battle is over, speak to Zathrian again. He will give you an item, and if you go back to the west Brecilian forest, you will meet a group of hunters who will reward you as well.

The Warden has the option to doublecross Zathrian, battling him along with four sylvian, two yellow shades, and the remaining werewolves. Zathrian does not regenerate between fights and will have very little HP remaining if he was significantly damaged or knocked out in the fight with Witherfang. This option gives you substantially more XP and loot than lifting the curse. Lifting the curse actually gives you no loot at all, aside from Swiftrunner's Shield.

Again, party members with strong moral opinions will react badly to this choice.

Convince both parties to lift the curse
If the Warden elects to talk it out with Zathrian and the Lady of the Forest, Zathrian can be convinced to sacrifice himself to lift the curse together with the Lady of the Forest. Zathrian will not accept without a fight, however, and will engage the party, the werewolves, and Witherfang (once freed from their paralysis spell). After Zathrian is defeated he will agree to help end the curse, the Lady of the Forest and Zathrian will both die, and the werewolves will return to their original, human forms. At this point the Warden may speak with Swiftrunner, now a human, who will thank the Warden for their help. If the Warden asks for a reward Swiftrunner will give the warden his shield. The Warden may choose to double-cross the now-human werewolves and slaughter them. They offer little resistance in their human forms.

The fight with Zathrian consists of two Greater Shades, several sylvans, and of course Zathrian himself, who is a powerful caster. The werewolves themselves cannot initially join in the fight because they are each encaged within a forcefield of sorts. To make the fight exponentially easier, have a party member cast a dispelling spell (such as Alistair's Cleanse Area) close to the werewolves to release them. Most of the werewolves should automatically engage Zathrian, interrupting many of his large AoE spells. Another strategy is to ignore all other enemies and focus on Zathrian. Note that the fight ends as soon as Zathrian is defeated; just hold out long enough for Witherfang and company to do their part.

Option for doublecross wherewolves: Make sure Zathrian ends the curse like mentioned above. Then when the wherewolves takes their humanform the dialoge starts. Choose the option " I demand a reward ". The humanform swiftrunner gives you the shield. Then choose the option " Not enough ". the former wherewolves now will attack you with there bare hands. Takeout swiftrunner first as he does the most damage. The rest does litte damage against your tank. Good loot afterward... few gold pieces and loot. You also get the swifrunner shield. As my char demands rewards throughout the game no one was disapproving (alistair/morrigan/wynne) at this point.

Party approval notes
Shale will disapprove if the Warden chooses to parlay with the werewolves. This can be made up after discovering (from the Lady of the Forest) that Zathrian has misled the party. Oghren will disapprove if the Warden does not kill Zathrian but is allowed to end the curse with the Lady of the Forest. There is no chance to make up the loss of approval. Alistair will approve if the Warden forces Zathrian to end the curse. Zevran strongly disapproves of the Warden attacking the elves, but he can be persuaded to not disapprove of the attack. As an alternative to forcing Zathrian, the Warden may also passively disagree to back him up on the matter, resulting in approval from Wynne.

Result
Once the curse has been lifted, not only are the ailing Dalish cured (if you did not kill them) but the werewolves again become human and immediately leave the ruin. If you sided with the elves, Lanaya (Zathrian's second) will agree to send troops to assist you in fighting the blight. If siding with the elves, once the werewolves have reverted back into humans, you can demand Swiftrunner's Shield as a reward. You are now free to explore the Forest to complete the Mage's Treasure Quest. The Mad Hermit's camp is now inhabited by bandits and the area beyond the forest barrier is now inhabited by reasonably-tough darkspawn.

If you decided to attack the Elves and side with the Werewolves, you will have Werewolves march to war with you at endgame rather than Elves. This will also mean losing access to the only infinite source of elfroot, deathrooth and toxin extract in the game, Varathorn. So stock up in advance if you intend to follow this path. Also, if you enter the West Brecilian Forest at a later time, you may run into the rest of the Dalish elves who will confront you.

Side quests
There are four side quests that can be taken in the Dalish Camp once Nature of the Beast has been started. Some of them cannot be completed after resolving the werewolf/elf conflict. None of them can be completed if you side with the werewolves (as all the elves will be dead).
 * Cammen's Lament &mdash; Ends upon return to camp if you did not visit Cammen prior to ending the curse. This quest is easily completed with a coercion skill of 3 though during your first encounter with Cammen prior to entering the Brecilian Forest.
 * Elora's Halla &mdash; Can be completed at any time.
 * Lost to the Curse &mdash; Speak to Danyla's husband before entering the Forest; complete by discussing her fate with him upon your return.
 * Rare Ironbark &mdash; Begin this before you enter the Forest; it will remain open after completing the main quest.

Some resolve themselves without player action if they are not completed before Nature of the Beast has been finished.

Codex objects
These entries can be unlocked in other areas before reaching this area.
 * One of The Black Vials
 * One of the pieces of Ancient Elven Armor

Bugs

 * Trading the Hermit for the Acorn will allow the Warden to loot the tree stump, receiving the Golden Ring instead of the Acorn.
 * After movie of the cure, you might not be able to exit; the doors somehow lose their activation icon. Save and reload game.
 * (XBox) Some players have reported a glitch where werewolf pelts disappear from inventory, preventing access to the ruins through the Hermit. Only matters if the player has already killed the Grand Oak.
 * Talk to the Grand Oak before killing the hermit (or checking the stump, which will force his death). If he dies first, you can be stuck without a way to complete the quest; the Hermit will be dead, the stump useless, leaving you no way to cross the barrier.
 * (PS3) When siding with the werewolves, it is possible to get blocked from completing the Nature of the Beast quest. Only Swiftrunner and Witherfang appear, standing near the forest entrance after the battle. This can happen when the battle ends prematurely if not all the elves in the Dalish camp are defeated. To ensure this does not happpen, make sure you run into all the elves by checking around the area. A cutscene should play shortly after all the elves are defeated.