Dark Gods and the chaotic fey of the Old Gods do not have temples like the more established gods of Vandalmál; their worshipers gather in secret to appease their dark deities and advance their agendas. These cults are usually small, often not even knowing of similar groups in nearby cities, taking orders from individual priests. Only rarely do such groups coordinate, but when they do, something terrible is likely about to happen.
Hel - the Eladrin goddess of the underworld, a dark, foreboding place of torment. Her cultists usually seek to enhance the fear of death by spreading diseases and sacrificing innocents. Intelligent undead exist outside of the natural order and have escaped Hel's grasp - her followers will usually seek to send intelligent undead to their torment and only use simple undead sparingly to further their aims.
Thrym - a wicked god of winter, also venerated by frost giants and feared by the Hobgoblin tribes of the Reaches. These cultists seek to extend the reach and length of winter to enhance their master's hold over Vandalmál.
Surt - the Eladrin god of war, also venerated by fire giants. While wars and battle break out occasionally through history, Surt is a deity who revels in the darker aspects of battle and conflict. His followers seek to destabilize governments and bring about violence between brothers, cities, and nations.
Aegir - the Eladrin god of storms and rough seas. These cultists can be found in coastal cities or in the Shattered Isles; they seek to spread fear of the seas, make shipping and ocean travel dangerous, and garner tribute from sailors for their god to help ensure safe travels.
Loki - existing outside of the courts of Eladrin gods, Loki is an unpredictable force of chaos. Loki's cultists are often as scattered and inscrutable as their god's motives.
Lord of the Bonfire - portrayed as an ancient, morbidly obese satyr, the Lord of the Bonfire is a spirit of dark debauchery. As the keeper of byways and a spirit of fire, his bacchanalia often appear harmless... at first. His adherents seek to engage in all manners of hedonism and depravity and bring others to their ways.
The Crone - a dark figure of Hrim, the Crone lurks in the shadows, making powerful deals and weaving dread curses. The Crone does not really have cultists - more petitioners... or middlemen: those who know the rites to call her attention to these poor unfortunate souls.