Before becoming a Companion, he fought in the Great War against the Thalmor before becoming critically injured in the fighting. After he recovered from his injuries he became a sellsword for hire across Skyrim. He eventually joined the Companions.
During the Proving Honor quest, the Dragonborn learns Skjor and the other memers of the Circle are werewolves. Shortly after their initiation into the Circle, Skjor helps the Dragonborn become a werewolf as well. However, he is killed by the Silver Hand when he ventures into one of their strongholds to scout it out for the Dragonborn and Aela.
Skjor, Kodlak, and Vilkas are the only Companions that wear wolf armor.
When the Dragonborn becomes Harbinger of the Companions, there is a chance that Skjor will be seen walking around Jorrvaskr. There are two version of this glitch- one where he follows the Dragonborn with his sword drawn and constantly initiates conversation, much like Aela the Huntress and Vilkas. In the other version, he simply says generic dialogue lines.
If you ask Ria why she joined the Companions, she replies by asking if the Dragonborn has heard the story of Kodlak and Skjor fighting one-hundred orcs, implying that he may have been the strongest Companion behind Kodlak.
In the Official Game Guide, his name is said to be "Skjor the Scarred".
PC 360 PS3 Skjor may still be found alive after being killed in the quest "The Silver Hand". He will continue to state that the Dragonborn still needs to prove his or herself, even after reaching the noble rank of Harbinger. He will wander around Jorrvaskr and act just like he did whilst he was alive. This may or may not be due to Skjor being part of a different faction, causing him to re-spawn when his character should die during the quest. Certain important characters re-spawn after being dead for one game month. In addition, he can also be found during a random encounter in the wilderness with a few other companions. He has been found both fully functional, and sometimes stuck in the ground, making no actions, but he can be interacted with. It is likely that after this encounter, he can be found once again in Jorvasskr, and will be able to give quests regarding "Speak to the Companions Leaders for work".
PC(Fix) Solution: Open the console and type disable after clicking Skjor.
Solution: You can kill Skjor and may or may not receive a bounty.
PC 360 PS3 Sometime after finishing the quest "The Silver Hand" Skjor may be found walking around in an area. He retains all of his equipment, moves around, but has no animations. Skjor cannot be interacted with, but he can be killed.
PC 360 PS3 Skjor's corpse may spawn, fully clothed in his room in Jorrvaskr.
360 Skjor may respawn in Gallow's Rock after becoming the Harbinger.
If a quest received from Skjor if he's back alive is successfully finished and the reward collected, the game may freeze on the loading screen when leaving Jorrvaskr.
In some cases, Skjor can be found dead in his room beside his chair. His wolf armor can be looted.
After installing a patch, and after completing the whole Companion Questline, Skjor is resurrected and his body on Gallow's Rock is removed. In addition, he is non essential, and can still give tasks.
Skjor can be floating around Darkwater Crossing without armor and his body halfway in the ground he also can be attacked but can't attack back and he appears to hold a leather shield. He also appears to be missing his right arm.
Using the Unrelenting Force shout against the bugged Skjor will result in him respawning nearby in normal form.