Upon reaching level 10, a guard at the city gate in Falkreath asks if a dog has been seen. Regardless of the response, reference is made to the local blacksmith, Lod.

Speak to Lod
Lod is located inside or in front of his forge. He has spotted a dog roaming near the city and could use it as a companion. Some meat is provided along with the task to catch the dog. With high speechcraft skills, a gold advance can also be acquired.

Find the Dog outside Falkreath
Thanks to the quest marker, the dog is quickly found on the road southwest of the city. Upon approaching him, he unexpectedly initiates dialogue. He introduces himself as Barbas and remarks that since Skyrim features flying lizards and two-legged cats, one should not wonder at a talking dog. He explains that his master and he had a falling out a few years ago and things became a bit heated. Barbas was cast out until he could find someone capable of settling the dispute. He quickly clarifies that his master is Clavicus Vile - the Daedric Prince of wishes. Apparently, his power is limited without Barbas, restricting his manifestation to the vicinity of his shrine. One such shrine is located inside Haemar's Shame, and Barbas requests accompaniment to that location.

Travel with Barbas to the shrine of Clavicus Vile ★
Barbas turns east, and one can attempt to follow him on the long journey. Keeping pace with him can become stressful. However, he can be caught up with at the bandit bridge or at the east gate of Helgen, where he courageously attacks every opponent.

The shrine is located inside Haemar's Shame, but can initially only be reached through Haemar's Cavern. These icy rock tunnels have been occupied by vampires of all kinds and their thralls. After fighting through the cold cavern, one enters the equally icy Haemar's Shame, where frostbite spiders also lurk alongside more vampires. Barbas provides active support while clearing the area. Once peace has finally returned at the end, Barbas waits patiently at the shrine of his master.

Activating the statue triggers the voice of Clavicus Vile, who listens benevolently, as one has already granted his worshipers their final wish - the cure for vampirism. In return, one can propose that he reunite with Barbas. Incensed by "the insufferable pup," he flatly refuses. Furthermore, one can ask him to end the civil war or grant the power to kill all enemies. However, since he does not currently possess his full Daedric power, he proposes a different trade: an exceptionally powerful axe must be brought to him in exchange for his blessing, and through this, Barbas could earn his place back at his side.

Retrieve the Rueful Axe with Barbas
The exit leading outside is located at the back of the shrine.
Rimerock Burrow is situated near the coast far to the northwest of the land and can only be reached via an obscure path. The small cave is inhabited by the mage Sebastian Lort and defended by a Flame Atronach. Sebastian received the Rueful Axe from Clavicus to cure his daughter of the werewolf curse. It now lies on a table not far from the mage.

The mage is a challenging opponent due to his magical shield and powerful shock spells. In the rear section of the cave, a few minor items and a Conjuration skill book can be found.

Return to the shrine of Clavicus Vile with Barbas and the Rueful Axe
Upon returning to the slopes of the Throat of the World, the path to the shrine can be shortened by climbing a little and directly entering Haemar's Shame.

At the shrine, Clavicus offers to leave his powerful Rueful Axe to the player if it is used to kill Barbas.

Give the Rueful Axe to Clavicus Vile OR kill Barbas with the Rueful Axe
A decision must now be made.

• Clavicus argues that Barbas certainly does not want him to have the axe. Therefore, Barbas would surely be glad to sacrifice his life. Furthermore, Clavicus claims he will absorb the spirit of poor dead Barbas, reuniting them once more. If one believes these words or absolutely wishes to possess the axe, the weapon must now be turned against Barbas.
  
  Speak to Clavicus Vile
  After Barbas is killed, Clavicus breathes a sigh of relief. He states that he has now regained his full power and no longer has to listen to Barbas's whining. While Barbas will return in 100 or 200 years, Clavicus intends to have plenty of fun without him until then.
  The axe is kept, and the quest ends here.
  
  
• Barbas is also quick to interject, explaining that the axe is not the only thing Clavicus possesses. If the axe is given to Clavicus, Barbas and his master will be reunited, and the player will receive the Masque of Clavicus Vile.
  If the choice is made to return the axe, Clavicus reacts angrily but takes Barbas back to his side, thereby restoring his full power. Due to a perceived lack of imagination, he contemplates turning the player into a worm. However, having more interesting matters to attend to, he hands over the Masque of Clavicus Vile instead, and the quest concludes.

Tips & Notes

• Lod can also be approached directly to learn about the dog during conversation. In this case, the preliminary objective "Speak to Lod" is bypassed.
• Clavicus Vile - the Vain or the Hideous - is the Daedric Prince of power-granting and wish-fulfillment through ritual summonings and pacts. He is usually depicted with his hound, without whom a portion of his power is missing.
• Among the vampires, one also encounters the paranoid and cruel Volkihar, who are allegedly capable of grabbing their unsuspecting victims through the ice of frozen waters.
• Aside from a few weapons and armor pieces, some valuable potions, a blood-splattered arcane enchanter, and an alchemy lab can be found within Haemar's Cavern and Haemar's Shame.
• Prior to starting the quest, a nameless leveled conjurer occupies Rimerock Burrow instead of Sebastian Lort.
• If neither the axe nor the Masque of Clavicus Vile is urgently needed, the quest does not have to be completed. Once the assignment for the axe is received, Barbas follows as a loyal protector. Barbas cannot be killed by anyone other than the player and serves as a valuable asset in addition to a regular two-legged companion. However, he can also be annoying, as his nose-nudging constantly displaces the player character.
• To achieve the Steam achievement "Oblivion Walker", the axe must be returned, as it does not count as a Daedric artifact. The only exception is if one has acquired both of Hircine's artifacts instead.
• If Barbas is told to stop following, he strolls back to the shrine slowly. If the choice for the axe is then made at the shrine, Barbas must be located outside. Fortunately, the quest marker remains active.
• Upon returning to Falkreath at any point, the blacksmith Lod can be asked if he still remembers the dog he wanted. One can explain that the dog caused too much trouble and the effort would not have been worth it. Lod understands and shows his gratitude with a small amount of gold.