the Nords or Vikings
The capital of the Faction will be the city of Shalassatanal
These are northern peoples who sail the eastern sea. The cult of Shalassa has always been strong in the lands of the Nords - this determined their fate.
Around 700, the Nagas from the eastern islands fell into heresy and decided to drown the godless empire, but they were quickly driven to the bottom by the Ice Legion. After some time, purges began in the north; the warlike Nords defended their traditions, and they paid the price - the emperor punished the north for disobedience by brutally suppressing the rebellion.
During the plague, all the mages of the north died, and then the Nagas emerged from the sea and declared that the sea goddess had punished the godless. The north revived the worship of Shalassa and began to wage war against all maritime powers (primarily against the demons who had occupied the eastern islands).
The Nords are ruled by Jarls, and Naga-Medusas act as advisors to the Jarls - these are the only creatures that freely use magic in the north.
Ideas
there is a mention that werebeasts are created with the help of dragon blood crystals; perhaps the Nords have some kind of ritual to transform into a monstrous werebeast, for example, a warrior must kill a wolf with his bare hands and bring its corpse to a shaman who will organize the transformation into an Ulfhedinn - a wolf warrior.
it so happened that the first Necropolis was destroyed by the Nords, and modern Necromancers are Nords; you can add undead to the Faction - drowned men, or Draugr, or both.
mages are the main enemies of this people, and perhaps they will have mana-draining monsters in their service