No One Escapes Cidhna Mine

After completing The Forsworn Conspiracy, the Markarth city guards frame the Dragonborn, starting this quest. The Dragonborn is locked in Cidhna Mine and at one point is given the choice to free Madanach and become a Forsworn or not. As a reward, the Dragonborn can either receive either the Armor of the Old Gods or the Silver-Blood Family Ring.

Quick walkthrough

 * 1) Ask a prisoner about Madanach, then get past Borkul the Beast.
 * 2) Talk to Madanach.
 * 3) Speak to Braig and listen to his story.
 * 4) Return to Madanach.
 * 5) Options
 * 6) Kill Madanach and leave Cidhna Mine through the secret escape path mentioned in Madanach's note.
 * 7) Kill Grisvar the Unlucky and follow Madanach.

Meeting Madanach
Talk to Uraccen to learn that Madanach is in a private cell which is being guarded by Borkul the Beast. Borkul will demand a shiv as toll. A shiv can be obtained from Grisvar the Unlucky, who is located in the south tunnel. He will demand a bottle of skooma. This can be obtained from Duach or Braig, through pickpocketing, persuasion, or a brawl. Return the Skooma to Grisvar in exchange for a shiv, and give the shiv to Borkul to obtain the key to Madonach's cell.

Alternatively, Borkul can be persuaded, given the skooma directly, or defeated in a brawl.

Attacking Borkul outside of the brawl will cause all the prisoners to attack, unless one is a strong mage character, a werewolf, or a vampire lord, this is not recommended. If a prisoner is attacked, Madanach will attack on sight as well.

The Forsworn Option
Madanach will try and convince the Dragonborn that he and his Forsworn are justified in their actions and sends the player to seek out the prisoner Braig and hear his story. After listening to Braig, return to Madanach and he will offer freedom, but he requires proof of loyalty. He requests the assassination of Grisvar the Unlucky, who has outlived his usefulness to the Forsworn Rebellion. After killing Grisvar, the Dragonborn must return to Madanach.

Upon hearing news of the Grisvar's death, Madanach gathers the remaining prisoners and leads them to an escape tunnel that runs through the Markarth Ruins. At the end of the tunnel, the Dragonborn's belongings are returned to them by Kaie, and Madanach rewards the player with Armor of the Old Gods. Once outside, there is a confrontation between Thonar and Madanach. The Forsworn and Madanach charge the city, killing Thonar and all guards (and citizens) in sight. After they leave the city, they will continue running to Druadach Redoubt which will have several friendly Forsworn inside.

The Silver-Blood Option
Kill Madanach with a pickaxe in his cell while in sneak so as not to be detected by the other guards and cell members, read the note on his body and use his escape route. It is advised to simply run past the Frostbite Spiders and Dwarven Spheres in the Markarth Ruins or if one has the ability to become a werewolf, it is rather easy to get past the dwarven spheres and the frostbite spiders by fighting them or sprinting past them. Upon exiting, Thonar Silver-Blood will reward the Dragonborn with Silver-Blood Family Ring and your belongings. The ring is enchanted so that weapons and armor can be improved 15% better.

Playing Both Sides
Side with Madanach up until the Dragonborn is given the Armor of the Old Gods, which is at the end of the Markarth Ruins right before exiting to the city. After the dialogue and receiving the armor, attack Madanach, turning him hostile. Doing this while close to the door to Markarth will cause his followers to re-enter and attack the Dragonborn. After the player kills Madanach and his followers, loot his body and read his note. Then exit out to Markarth and speak to Thonar. It is recommended that the player attacks Madanach close to the door to Markarth because if not, his followers may not re-enter and it can be difficult to get the Silver-Blood Family Ring from Thonar as Madanach's followers will be waiting outside to attack.

If done correctly, after killing Madanach and the rest of his Forsworn followers inside the Markarth Ruins, the player will exit out to a peaceful Markarth with Thonar waiting to speak with the Dragonborn and reward him/her with the Silver-Blood Family Ring and a pardon from the Jarl. If the player speaks to Jarl Igmund afterwards, he will apologize for the wrongful imprisonment.If upon exiting the tunnel there are Forsworn left, it helps to reenter the tunnel so that you do not accidentally hit Thonar.

If the player is a skilled assassin, they can break out with the other Forsworn, and stall Madanach before he exits to Markarth. Once alone with him, you can cut his throat and search his body. Madanach will be dead, but the player won't be blamed for the kill. When you exit to the city, both the Guards and Forsworn will be peaceful towards you, although they will still fight each other - the player can assist either side, as both are friendly and will treat any attacks as accidental. Thonar will almost certainly be killed in the fighting before he can give you the ring, but this route still leaves the player with the Armour of the Old Gods, an official pardon from the Jarl, a friendly Druadach Redoubt, and another dead Silver-Blood, making it extremely satisfying. It may take several attempts to pull off properly, however.

Another way is to stall Madanach and pickpocket him. He turns aggressive and can be killed. A guard will run in but will not attack.

Another way, is cheating a bit, but it will reward both the ring and the armor. Pickpocket the key from Borkul, and go see Madanach. After talking with him, take the wooden pate on his table, place it against the bars on the locked cell, and run through it. Follow the tunnel into Markarth Ruins, and follow to the end. Madanach will show near the end. Talk with him to receive the armor and your belongings, then attack and kill him. His followers will then  appear, kill them also. Then exit to a peaceful Markarth and talk to Thonar. He will then give you a pardon, and his ring.

Notable loot
There are two main paths for escape, and each carries a reward:
 * Helping Madanach by killing Grisvar rewards the Armor of the Old Gods, a full set of enchanted Forsworn Armor (Light Armor).
 * Madanach's new headquarters at the Druadach Redoubt cave contains more valuable loot, free for the taking, and a map of all Forsworn encampments.
 * Killing Madanach and escaping alone rewards the Silver-Blood Family Ring, providing +15% Smithing.
 * If the player kills Madanach after receiving the Armor of the Old Gods and their belongings, but before leaving the Markarth Ruins, Thonar will greet him outside with the Silver-Blood Family Ring and the quest will be completed.
 * Once you have completed the quest, bear in mind that the body of Eltrys is still in the Shrine of Talos and can be looted for several hundred septims.

Trivia

 * The Dremora Butler can also smuggle in items for you.
 * Ironically, Cidhna Mine is escaped through a large, extremely visible hole in the wall that leads straight to Markarth. The Markarth guard, however, seem to be fairly aware of it, since you come out right into the hands of the owner of the mine himself, accompanied by guards, who were waiting for you.
 * If the player killed Madanach and is going through Markarth Ruins solo, a good way to beat the spiders and Dwarven machines is to run past the spiders until reaching the last room, where the Dwarven Spheres attack, then lead them back to the spiders to have them fight each other.
 * With a high Pickpocket skill, one can reverse-pickpocket Urzoga gra-Shugurz beforehand and smuggle equipment into the mine though you must be in reach to pickpocket her through the bars as the door instantly shuts as she begins walking.
 * Also, it's possible to shove Urzoga into the mine with you though for no apparent reason, whether to pickpocket her equipment or to simply kill her with the prisoners' help.
 * If you choose to kill Madanach, and you are a Nord, he will say "Come at me son of Skyrim!"
 * If you wish to complete the quest but avoid directly killing Grisvar, you can choose the 'Madanach says hello' dialogue option and wait. Grisvar will panic and start attacking, and the other prisoners attack and kill him.
 * If you choose to not side with any prisoner, you might have a hard time killing them all with just a pickaxe. But there is a trick to it. If you walk up on the hanging bridge and wait for them to stand directly in front of you, you can use the Unrelenting Force Dragon Shout. The prisoners will then fall off into the pit directly behind the bridge. The NPCs can't get out, but the player can, making it easy to pick them off one at a time. You could also transform into a Werewolf if sufficient progress is made in the Companions' questline, or buy the spell Bound Sword or any spell tome used to summon a familiar beforehand from a court mage.
 * At one point in the mission, the player is asked if they have any family, and can respond that they are outside Skyrim, that they are all dead, or that they don't have any that they care to talk about. This is perhaps the only time in the game where the Dragonborn can talk about their previous life. This has changed with the release of the DLC Dawnguard. Serana, arguably the main Dawnguard follower, will ask about the Dragonborn's family during a discussion of Serana's family.
 * When talking to Madanach for the first time, choosing the dialogue option 'How about revenge?' sometimes causes only him to attack. After killing him, the other prisoners will act normally.
 * Despite Cidhna Mine being considered a prison at the start of the mission, completion of the quest will not reward the "Wanted" achievement.
 * If you have a follower, like Lydia, before you go back into the Shrine of Talos to get caught, give her your equipment and ask for it in the mine and kill everyone.
 * It is highly advisable to gain the Silver-Blood Family Ring (whether by sticking to the Silver-Blood side or by playing both sides) as it is one of the only items enchanted with "Fortify Smithing". A skilled enchanter can disenchant this item, and create (for example) a necklace and ring which both raise smithing by 25%. By doing this, one can upgrade any item that does not fall into a specific smithing category (Nightingale Armor, most daedric artifacts) to "legendary" status without the need of smithing potions, which are rare and often hard to aquire.

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