Two Worlds Pacifist Run - Karga Clan Territory

The elusive Karga Clan rebels are said to have a hidden fortress somewhere in the northern mountains of Thalmont, but their nemeses in Skelden House don't know where it is. However, you can find the Karga Clan territory yourself fairly easily by exploring the northwest: The easiest route is probably to ride up the mountain paths north of Covengor village, or to descend from the high slopes west of Throglin Temple.
Tunnel to Karga Fortress, seen from ridges above the main road leading up from Covengor environs
However, if you haven't earned any reputation with Karga Clan yet, the fortress guard will not let you inside the locked gates. The same is true if you find the Karga Supply Cave (required to solve Sanno Moon's quest described in the EXCAVATIONS section.)
One easy way for a pacifist challenger to do this is to talk to Eras Brakalet outside Pale Stone Cave south of Thabarkin (see THABARKIN section for details) and complete his easy quest to unlock a gate in the cave. Another longer option would be to journey over the mountains a long way into the wilderness east of the Excavations, where you can find Conn Krannach for another nonviolent quest (described in the section on the Eastern Mountains and Grom War Camps).
After this, whichever Karga man you helped will vouch for you, and most other Karga men you talk to in future will consider you a friend.
If you take the route by travelling the mountain roads north of Covengor, however, you'll also find several other potentially important stops before you reach the Karga Fortress:

Northwestern Grom War Camp
Whether or not you're ready to start dealings with the Karga clan, there is also a Grom War Camp high up in the hills northwest of Covengor, above the old graveyard and the necromancers' hut. Here you will find more Groms and a sacrificial rockpile with magnesite (which you can take back to Ferid Redismos for more teleport stones, if you haven't already gotten all three), a horned totem (which you can bring to Skelden House officer Menno Heragerard later for his quest), and also a mage staff lying on the ground near the mound. (If you've already been to Thabarkin Town, this is the staff sought by the friendly old mage.)
Visiting the Northwestern Grom War Camp, hiding behind the war totem mound in sneak mode...
The Groms also have stolen someone's horse, which you can steal back for your own use if you don't mind breaking your cover long enough to jump on and ride away to safety, but will likely be struck by a few Grom arrows while making the getaway...

Karga Supply Cave
Further up the main road north of the side-path leading to the Grom War Camp, there is another sideroad leading up into the western slopes will bring you to a Karga supply cavern that is locked and gated, guarded by a Karga warrior named Serpen.
The Karga Supply cave...
If you approach without first having gained some reputation with the Karga Clan, Serpen will turn you away brusquely. However, if you've completed one or more side quests to gain reputation with the Karga Clan, he'll greet you and allow you to freely enter the cave.
If you've already visited the Skelden Excavations and received Sanno Moon's subquest "The Cure," this is where you'll find the mysterious medicine Moon wants so badly.
(As far as we could figure out, the cure is also the only thing you can actually take from the cave after Serpen invites you to take supplies.)
Once you have it, all you'll need to do to finish Moon's quest is to take it back and hand it to him at the Excavations (but will probably also want to talk to the missing courier Estar Gren for even more nonviolent xp rewards in Gorelin, if you haven't been to Gorelin already).
Once you have the mysterious "Cure," handing it to Moon will reward you with xp and Moon's support in House Skelden.

The Hidden Fortress of the Karga Clan
When you're ready to continue the Karga & Skelden faction intrigues by visiting the Karga Fortress, you can find it by following the main road leading north into the mountains, which will eventually enter a natural stone tunnel in the rockfaces. This leads to a guarded entrance to the secret Karga Clan fortress.
There is a guard at the gates named Marcas who will let you inside if you've gained reputation with the Karga Clan. (Note: If you want to be humane toward humans and animals alike, you'll want to use stealth or freezing magic/earth chains, etc to make sure no bears and wolves chase you up the pathway through the tunnel, or else they might end up being dispatched by Marcas near his post at the gates.)
The Karga Clan Fortress gates...
Once you're inside the Karga Fortress, there are many more nonviolent subquests you can solve:

A Karga man named Barra will give you a quest to hunt down and kill an alleged traitor named Isa, who betrayed the Karga hero Conn Krannach and caused the latter to go into refuge.
However, Isa happens to already be dead, which means you can go find his body in a cave full of wolves only a short distance north of the tunnel, nonviolently evade the wolves after making the discovery, and then return to claim the 5,000 gold reward from Barra. (Whether Isa really betrayed Krannach and why he did so remained a mystery on our playthrough, but Barra will still give you the amount of gold promised as bounty.)
Barra, who will pay a large bounty for the discovery of the alleged betrayer Isa...
"Sources Drying Up"
This is a simple quest from a Karga healer named Antrai, who says he lacks alchemical skills and wants two healing potions to use to lend strength to his own mixtures. If you give him the potions, it will complete the quest and he'll give you a Blizzard spell card as a reward. (This spell isn't very useful in a pacifist challenge since it just rains down ice-damage on foes, but at least you did a good deed.)
The mage Antrai, who left the Society to work as a healer at the Karga Fortress...
"Collecting Evidence"
Also on the main lower grounds of the fortress, you'll meet a Karga operative named Ethan who looks very similar to Barra. Ethan will reveal that they have a spy named Zed Masara giving them information on Skelden's activities. (If you already spoke with Eras Brakalet outside Pale Stone Cave, that youngster will already have revealed Masara's name to you even before you finished his quest to open the Thabarkin passageway.)
Ethan, who gives the 'Collecting Evidence' subquest, looks like the twin brother of Barra, but is a different NPC.
Ethan will engage you to go to Gorelin and get some Excavation reports from Masara, and bring them back to him. However, in order to get into Gorelin Village to talk to Masara, you'll need to gain reputation with the Giriza first. As explained in the Gorelin section, Gorelin is a stronghold controlled by the Giriza Thieves' Guild, and the gate guard Met will only let you in if you've gained some reputation with their faction. We did this by completing quests for the Giriza operatives Stork and Keshi Lono who are lurking outside the Inn south fo Thabarkin Castle, though there are other ways. (See the sections on the Thabarkin Crossroads Inn and Gorelin for our way of doing this on a pacifist run, which will involve intrigues with the Giriza, Skeldens, and Karga Clan all at once by the time the sequence is done, but no fighting.) Once you've got the Excavation reports from Masara, you can bring them back to Ethan to increase your reputation further with Karga Clan.

Ultar Karga's Hideout & The Karga Treasury

If you follow the main road through the inner walls of the Stronghold and up the craggy switchback path leading north, you'll come to an upper level of the stronghold containing the Karga Treasury and guarded buildings where the clan's leaders Ultar Karga and his son Cahal can be found.
The Karga Treasury is where the golden relic frame needed to eventually complete the main storyline quest sequence is stored by the Karga clan, but you'll only be able to open the treasury later, after choosing to decisively aid either the Karga Clan, or their nemeses the House Skelden.
The relic frame inside the Karga Treasury (which you can only access later, after concluding the Karga vs Skelden saga).

Ultar Karga's building is guarded, and the guard won't let you in without getting permission from Ultar's son Cahal first.
Cahal is found outside another building a short distance ahead. He is convinced the clan's honor requires that House Skelden's leader Erbat Skelden be killed, and he is upset because his father has plans to restore the clan's position as the regional governors of Thalmont by finding proof of Skelden's corruption, rather than shedding blood.
Talking to Cahal will give you the quest "Eye for an Eye" requesting that you kill Skelden yourself to avenge Cahal's take on the Karga honor, but in the end you can simply ignore Cahal's demands for blood. (There won't be any penalties for letting Skelden live, other than upsetting Cahal, who will bluster at you a bit, but won't attack.) Once Cahal believes you've agreed to kill Skelden for him, he will tell the guard to let you inside Ultar Karga's lodge to speak with his father.
Ultar Karga will reveal that the House Skelden has discovered a secret gold mine, but never told the King about it even though the realm is wracked by warfare. Furthermore, they have learned that a former moneyer to the Crown (a man named Net Tannos, who you never directly encounter as far as we know), was believed dead, but has also been seen among the Skelden forces.
Ultar Karga is convinced that there must be some proof at the excavations of a conspiracy to strike golden coins without royal authority, which would be sufficient to have House Skelden ousted in a scandal, restoring the leadership of Thalmon to Clan Karga.

This leads to a quest called "A Final Strike" in the Questbook.

When you're ready to conclude this quest and bring the Karga Clan vs Skelden House saga to an end by choosing which side to take, you can find the details in the separate section on Karga vs Skelden. However, be warned that there are a number of rewarding nonviolent pacifist run quests to complete for both sides before doing this. (Even though you won't have to kill anyone or cause any deaths if you end up taking the Karga side, the Skeldens will leave Thalmont after the drama concludes, and you won't be able to finish any of their side quests after that.)