Unseelie fey are typically seen as the "nastier" of the courts in comparison to the Seelies, mostly because the malevolent acts of the Unseelies are done more openly. Also, according to Sallows, Unseelie Court faeries do not like too much light.
The symbols of the Court include a hawk, a throne, and a broken crown. The King's main insignia is the broken crown symbolizing his belief that he should be ruling both Courts of the Fair Folk.
The Unseelie Court is a mobile location, not always found in the same place and moves around the Unseelie Lands. In 2012, at the time of Kieran's planned execution, the Court was in the darkest part of the forest, with tents and booths clustered in a glade in a circle of thick trees. The main part was a massive draped pavilion, with banners of the Unseelie King's symbol hanging from every part of it, and a single tall, black stone throne, on the back of which was carved the King's symbol hanging above a moon and a sun.
For a long time, the Unseelie Court typically did not involve itself in outside affairs, such as the Shadowhunters or their Accords, and are not very interested in even trying to be in good terms with them.
When the Cold Peace commenced, however, the Court felt its effects because of the severity of the imposed laws of the Shadowhunters. In retaliation, the Unseelie King initiated a series of events in preparation for an eventual war against the Nephilim. The main power of his plans stemmed from his partnership with Malcolm Fade, who performed spells for him that weakened the Nephilim. With magic provided by Malcolm, the King had portions of his land "blighted", rendering Shadowhunter magic, weapons, and gear useless.
The blight and the King's attempts were first noticed by the Shadowhunters in 2012, by a group of young Shadowhunters from the Los Angeles Institute when Malcolm's deceit was discovered. Apparently in fear of their growing power—along with wanting the Cold Peace to end—the Seelie Queen promised her aid to the Nephilim against the Unseelie Court if war came.
- Though one has not yet been introduced, The Shadowhunter's Codex features an illustration of an Unseelie Queen.
- In most real-world mythologies, the Unseelie Court is also often seen as the classification given to "evil" faeries; though since the Seelie Court has been known to be quite malicious, the Unseelie Court is usually seen as darker and more inclined towards unprovoked assault. However, the beings of the Unseelie Court are not always malevolent, but when an Unseelie faerie is forced to choose, they will naturally prefer to harm than help.
- In mythologies that categorize faeries into six courts, the Unseelie Court is often considered "dark", a combination of the Winter and Autumn Courts.