Akthanakos' memory is a book found during the Mahjarrat Memories miniquest. When Akthanakos' memory is brought to Kharshai, he transcribes it into the book. To find it, a fully charged Engrammeter must be operated inside the final room of Enakhra's Temple, where Akthanakos was found in the Enakhra's Lament quest.
Senntisten was the centre of the empire. I spent far less time there than some of my lazier kin, but between campaigns I had the opportunity to witness its fits of growth as it spread across the land. In the time before Zaros, at the dawn of the Second Age, Senntisten was a primitive human settlement much like any of the others that dotted Gielinor. It and the villages around it were ruled over by Loarnab, a many-headed god of limited intellect but tremendous might. Zaros's legions trapped Loarnab and Zaros used his magicks to twist it into a living power source for his forces. The arrival of thousands of demons, and the torture and imprisonment of their god, so intimidated the people of Senntisten that they didn't even try to fight. They bowed down in worship of their new ruler.
Zaros's legions spread outwards conquering more and more of the human tribes, but he remained in Senntisten and made it the centre of his civilisation. He converted almost all of the village's population into his priesthood and had them trained in religion, law, the Infernal language and such matters. Many of these priests he sent out to the newly conquered territories as emissaries, missionaries and bureaucrats, and so the empire rapidly spread and civilisation emerged. Senntisten itself took tribute from the rest of the empire as its population of priests and jurists could not support itself. The population continued to grow, though, as pilgrims and the disaffected from all over the empire flocked there. The streets became filled with elaborate temples, many of which were schools or seminaries or courts or offices.Through the church Zaros taught the empire many secrets of agriculture and industry and architecture, and Senntisten was always the first beneficiary of each advance. Great halls and towers and aqueducts sprang up over the city and the lands around were filled with efficient, irrigated fields, mills, jennies and straight, well-maintained roads. The population continued to rise uncontrollably and the proportion that belonged to the clergy or the military fell and fell. More and more so, the humans devoted themselves to the provision of luxury and services for each other. The city had become its own purpose, not just an administrative centre but a great living creature in the centre of the empire. I asked Azzanadra about this, and he told me that Zaros seemed pleased by it, not a sentiment we associated with our lord. When I stood on the walls of the Basilica at night and looked out over the city, though, I felt exactly the same way.