Technically speaking, she was not a member of the System Lords but possessed a fearsome reputation due to the minions she possess. This was because Selket was the mastermind that created the fearsome Ashrak and it was her that organized as well as handled their training which quickly produced an army of elite killers.
Beyond her private army of assassins, Selket possessed little else in terms of power. She did not have to expend much in terms of resources to maintain her domain for she believed that this did not depend on Jaffa or Ha'taks. Her power comes in the form of respect as well as the fear generated from her army of Ashrak who could easily bring down a rival Goa'uld Empire by the hidden blade of her assassin warriors.
Not surprisingly, this generated a deep-seated paranoia in Selket which may have proven to be her downfall. This intensified after the lesson that was generated by the rogue Ashrak Marduk and the fact that he was entombed by his own Jaffa made Selket even more paranoid that such a fate could befall her. This resulted in her making new security protocols that even the other System Lords thought were excessive.
It was rumoured that Selket employed brainwashing and post hypnotic suggestion techniques on her newer generation of Ashrak in order to ensure none of them went rogue. This would generate some rivalry between herself and Olokun in a form of competition on who would excel in the role of information gathering and espionage.
Selket's appearance was somewhat unknown as she was known to constantly change her host. On some occasions it was known that she would change hosts on a monthly basis with the former hosts being ritually killed to ensure no loose ends were present. It was Selket who pioneered the techniques in suppression of the host consciousness that allowed Ashrak to quickly dominate new minds easily when infesting new bodies. As such, her recovery time after taking possession of a new host body was far shorter compared to other System Lords. Only her closest advisers knew her latest host's identity. Before her new identity was revealed, however, it was known that she would use that short time to inspect her followers who were unaware that Selket walked among them. She would then personally accumulate intelligence on the unsuspecting followers and would attempt to subvert any attempts at treachery.
Tok'ra intelligence believed that it was Selket and her assassins that were responsible for the capture and imprisonment of Egeria by Ra over 2,000 years ago. She was contracted by the Supreme System Lord to capture the rogue Goa'uld queen who had spawned her movement against the Goa'uld Empire. This helped her regain some of her lost power after the mad killing spree made by Marduk. The Tok'ra were known to keep tabs on her to ensure that they were aware when Ashrak were dispatched against them. It was known that any Tok'ra caught in her domain were ruthlessly tortured before being destroyed.
Selket's personal life was largely unknown though it was rumoured that she kept Jaffa as well as human consorts for short periods of time but there was no confirmation on this. This was primarily because of the fact that anyone who entered Selket's court was never seen again. It was also known that she did not have many personal enemies due to the fact that her business with the System Lords made her a necessary part of the Goa'uld Empire. Despite the fact that some Ashrak can be 'bought' or contracted out permanently to a System Lord, their first loyalty was to Selket. As such, they would not move against her or betray her whereabouts to others. This was perhaps both out of fear and the indoctrination techniques used on them. It was rumored that one Ashrak attempted to break ties with Selket about 300 years ago and was hunted down by another Ashrak six years later. It was said that scattered remains of the hosts body as well as symbiote were spread across five separate star systems.
Selket was known to rarely associate herself with other Goa'uld outside in her duties of assassination and intelligence operations. In fact, it was known that she possessed few true allies among the System Lords. However, the support she does gain was enough to ensure that other Goa'uld did not move against her. These supporters included Lord Yu, who makes rare but necessary use of Ashrak, and Morrigan who enjoyed the terror that the Ashrak would bring to her enemies. (RPG: "First Steps: The Stargate Unexplored Worlds Roleplaying Sourcebook")