|Date of occurrence:||December 2007|
|Participants:||Shadowhunters and Faeries|
|“||If this was peace and victory, maybe war and fighting was better after all.||”|
- Magnus Bane: "I hear things, rumblings in Downworld, the rumor of coming strife. The Fair Folk are a proud people, the proudest; they will not take the shaming from the Clave without retaliation."
- Catarina Loss: "They are proud but patient. They may wait a long time, generations, for vengeance. You cannot fear it coming now, when the shadow may not descend for years yet."
- ―Magnus fearing the faeries' retaliation, City of Heavenly Fire
For the war, the Seelie Queen decided to side with Sebastian Morgenstern, the enemy of the Nephilim. They provided them with protection, faerie warriors, and means to strengthen their numbers. For their role in the Dark War—a war Sebastian and the faeries ultimately lost—and their involvement with Sebastian, the Clave announced a set of sanctions against the Fair Folk that would apparently keep their relationship as amicable as can be.
With Kaelie Whitewillow as the representative of the Seelie Court, the Court agreed to the Clave's demands and pleaded for leniency to avoid a war. The faeries lost their seats on the Council. While the demands were difficult for them to fully accept, and even the warlock representative Magnus Bane objected to the terms of the treaty, Kaelie was left with little choice and eventually did.
The Clave's sanctions against the Fair Folk included the following: the faeries would pay reparations for the loss of Nephilim and Downworlder life as a result of their attacks on the Institutes and the Praetor Lupus; they would no longer be allowed to have armed fey warriors or armies, and any of the fey who were seen bearing weapons without Clave approval would lawfully be killed; and, they would no longer be directly protected by the Clave under the Accords.
Later, the warlocks Catarina Loss and Magnus discussed how they had heard rumors in Downworld that the Fair Folk would someday seek revenge on the Nephilim and the Council for their sanctions, though they admitted that the fey are a proud and patient people who may be content to wait years, or even generations, before seeking vengeance. The tension between the Fair Folk and the Shadowhunters after the Dark War became so severe that even their own half-fey Shadowhunters were caught in the cross-fire, resulting in Mark Blackthorn being abandoned to the Wild Hunt, and his sister Helen Blackthorn being posted to Wrangel Island to study the wards.