SkekNa the Slave Master was the dark half of the Mystic urNol the Herbalist. Together they made the UrSkek NaNol.

From the moment he came into existance, skekNa was openly evil, despising all the creatures on Thra, where as the rest of the Skeksis kept their nature and intentions hidden. He was skeptical of skekSo's leadership when he began his machinations for the gentle races, though he was silence immediately when skekShod was beaten by the Emperor when the future treasurer scoffed at his title openly in court. As punishment for their defiance he, along with skekShod, were ordered to do the remodeling of the Castle with stone panels.

His futher defiance may had lead to the lost of his right eye at the hands of the Peeper Bettle: in Age of Resistance, when the Scientist was about to be punish with the creature, skekLach alludes to the fact no Skeksis had seen it in many Thrine, possibly skekNa having been the last victim as he was the only other Skeksis to have a missing eye, and the Chamberlain revealing to Gurjin that they used the Beetle only on the Skeksis that misbehaive, covering it with an eyepatch since. There is no yet canon explanation how he lost his Left arm (or finger, urNol having only a splinttered finger), but he replace it (or hide his minor wound) with a Mechanical Hook. His face was covered with straps and his right gaunlet had sharp hooks. These traits made him the more identifable of the Skeksis at plain sight.

He seems to respect or, more likely, fear strong leaders: when the Skeksis first started to insert their influence, skekNa became a subordinate of skekVar the first General, joining him and some of the battle able Skeksis with the Gelfling to destroy the Mahkraks, before they were stopped by the powerful chant of the Mystics. Afterwards the Crystal Alliance was established and SkekNa became part of the skekVar Alliance along with skekZok and skekAyuk, and perhaps skekUng may had been part of this group, as the First General seem to respect Brute force: this may had forge the trust between Ung and Na, along which would force in their own alliance. Presumably, he was the Spy Master, but skekZok did describe him as useful in a fight along with Sa and Ung, when the Skeksis were considering to recall the others back to the Castle as the Hunter lay Dying.

While he had the respect of the Ritual Master, skekSil had a low opinion of him, indicating he lack nobility and imagination.

When the remaining Skeksis rejoined after the disastrous battle in Stone in the Wood, with further loses to their number, skekUng was ascended as Garthim Master and General, skekNa became his trusted subordinate from the age of the Garthim Wars and the Gelfling extermination till the downfall of the Skeksis, with the Scientist joining their alliance. After the Draining process was “perfected” to create mindless Slaves, skekNa was given command of these and was overtly abusive to them, beaten them at every turn, leaving bruises on them, or pulling them from their chains, almost choking them. He however picked the best promising specimens for the Poddling Choir, supposely having a talented ear for music, and would have Slave ready with Scraps to feed the Skeksis ravenous hunger.

When skekSo died, the surviving 9 Skeksis broke into factions, with Na supporting Ung to the throne along with Tek. When the Garthim Master won, he along with the other Skeksis attack and demoted the Chamberlain before the new Emperor banished him. For the remainder of skekUng's reign, skekNa remain loyal by his side, with the new Emperor considering to ascend him into a Patriarch, a position that would put him above skekZok and skekSil in the Skeksis hierachy, but he would never get the chance, as Jen healed the Crystal and the Slave Master was absorbed into the Herbalist, resurrecting NaNol into existance. Afterwards NaNol helped revive Kira and departed Thra with the other surviving 7 UrSkeks.

However, 100 years later, skekNa was brought into existance once more along with the other Skeksis, thanks to the Fireling Thurma, who cracked the Crystal in the hope of saving her world with its shard, been reborn with both his lost arm and eye in good condition. As the hunt for the Shard ensued, skekNa and the rest of the Skeksis created chaos in the castle, they were briefly held, but escaped thanks by the corrupt Crystalline Emminence. He would later find a Poddling and drained him of his essence. His rampage was stopped as the Crystal was once again healed, and Na was re-absorbed into Nol. The Now surviving 7 UrSkeks departed Thra once more, with a rejuvinated Jen and Kira, and Fizzgig, leaving Kensho and Thurma as leaders of their respected Clans.