They fall into a mystery that involves the fast deterioration of Seregil's mind and sanity, and Alec must find a way to save his new teacher and friend.
A plan to retrieve all the pieces of the helm is attempted by a Plenimaran, Mardus, who wishes to use it to conquer Skala and Mycena and rule over the three lands.
Using Alec's unique blood as a half-Northerner, half-hâzadriëlfaie, the alchemist intends to create a creature called a rhekaro, who appears to be a young child and yet is decidedly inhuman.
Its moon-white skin and frightening powers make it a danger to all whom Seregil and Alec come into contact with, leaving them no choice but to learn more about Sebrahn's true nature.
After being seduced by Ilar í Sontir into breaking atui during a treaty and accidentally killing a man, he is exiled to Skala by the rhui'auros request where he becomes a Watcher, a spy in the queen's service.
Mortally wounded by a Plenimaran arrow, she holds on long enough to send Princess Klia on the vital mission to re-establish relations with Aurënen—since she does not trust Phoria, her eldest daughter and heir, to do it.
Rhíminee was founded by Queen Tamir the Great (who was personally involved in the details of city planning) after the earlier capital Ero was destroyed by the Plenimarans.
There are the double walls forming a ring around the city, plentiful supplies ready for the possibility of a siege, and streets designed for defense against any attacker who might breach the outer defences.
This wealth is divided unequally—there is an enormous disparity between the rich quarters at the northern part and the slums to the south; Alec and Seregill are at home in both, with some preference for the poorer areas.
Inside are a huge living room with a dining area, a study, and many books and tools, filled with knickknacks Seregil has picked up throughout his travels and a large bedroom.
Originally intending never to return to a place with such painful memories, at the end of Traitor's Moon, Alec and Seregil decide they really do miss and need this home, so they will rebuild it.
Less than a day's ride north[citation needed] of Rhíminee, it is the land the royal family gave Micum Cavish in gratitude for his work as a Watcher for Skala.
Wars between Skala and Plenimar usually take place mainly on Mycenan soil, causing great hardship to the country's civilian population.
This makes the Golden Road a valuable economic and strategic asset, a regular bone of contention in the wars between Skala and Plenimar.
In the early Nightrunner books, the depiction of the Plenimarans is wholly negative—its soldiers habitually perpetrating atrocities and civilians at home maintaining extensive slave markets.
The final book, Shards of Time, introduces a positive Plenimaran character, a doctor who is humane, dedicated to healing her people, opposed to slavery and descended from a like-minded family.
Aurënen has no true central government, its inhabitants divided into numerous self-governing clans, each of which has divergent economic interests and considerable social and cultural differences from each other.
The closest they have to a central government is the Ia'sidra, a council of the eleven most powerful khirnari that meets at Sarikali, a holy city fully intact and abandoned by an ancient race—serving as neutral ground for settling disputes between the clans and for celebrations.
This, however, precipitated a reaction from Skalan bigots, who after the Queen's death assassinated her Consort—which in turn led to a counter-reaction by those in Aurënen who frowned at close relations with Skala.
They have a strong taboo against intermarriage or interbreeding with outsiders, any such act punishable by death and any offspring of such a relationship are ruthlessly pursued and killed.
Later the Hâzadrielfaie's point of view is given and the reason for their behavior is revealed: their blood could be used to make creatures called Rekharos, who have enormous healing power.
In The White Road, a band of Hâzadrielfaie come into greater contact with the outside world than they had for many generations, and are forced into alliance with Seregil, Alec and Micum—which lessens their prejudice, if only a little.
The settlers arrived about 1500 years before the time of Serengil and Alec, first establishing themselves on Kuoros and then spreading in all directions, forcibly uprooting the Retha'noi and driving them off the sea and deep inland.
Male Retha'noi witches practice their magic mainly through the oo'lu, a nearly body-length horn created in a complicated and meticulous ritual process.
The same oo'lu music, however, can be turned into a deadly weapon by the addition of a single sharp note, severing the soul's link to the body and killing instantly.
Another application of oo'lu music is to hide the witch himself and people he wants to protect, and render them effectively invisible to pursuing enemies.
The Tamir Triad relates a period where Illior and Sakor (or at least, their human devotees) were in conflict and the Sakorans actively persecuted the Illiorans; by the time of the Nightrunner series, this breach is long forgotten.
Still, Sakorans are sometimes heard to express preference for their "straightforward god" who can be counted on to reward bravery on the battlefield—as compared with the countless subtleties and ambiguities of Illior and his priesthood.
On that occasion a single black bull is sacrificed by the Queen in person, in a major ceremony involving all of Sakala's civic and religious dignitaries.
The Mother is a fertility goddess and sex is part of her worship—in particular, making love in the open fields under the Full Moon, a practice that contributes to Skalan prejudice against the Retha'noi.