Evil,  tormenting, powerful  and cruel, these creatures have appeared on Golarian from a far dark realm some say as a result of Zon Kuthon.  Though they hold no allegiance or care for him or any other diety.  They plague the land and its inhabitants alike crafting cruel merciluous undead abominations known as the Cryx,  out of every thing they capture.

They seem to take over abandoned settlements where they can continue their perverse experiments.  Cephylix use powerful psionic necrotics to create legions of servants known as Cryx to carry out their will.   Their powers of the mind are formidable and they can sense thoughts and twist your will. Their favorite pastimes is cultivating humanoids into their drones through dark psionic experimentation. 

Battle of Dinyar

Over 150 years ago the Cephylix with their Cryx minions began expanding south from their stronhold into southern Isgar in the Aspodell Mountains. A mixed band of Eagle Knights, Hell Knights and the entire Order of the Palantine Eye banded together. The slaughter was devastating on both sides but they were able to push back and contain them. The order of the Palantine Eye was completely wiped out but the few remaining Hell Knights established the Citadel of Dinyar in Isgar to keep a watchful eye over the region. 

(DM's Note: Necron is power behind Cyphelix and Cryx)