Unseelie get access to the GLAMOUR power, which can allow Unseelies to use their unpredicatable faerie magic. The more powerful the Unseelie using the glamour, the more effects he can create — from create faerie food to faerie rings, turning invisible and changing shape. Unseelie can only use this power when indoors. Most importantly, Unseelie can only use their glamour during the twilight hours of just before dawn and just after sunset.
Unseelie gain in strength, dexterity, and perception during the twilight hours and are weaker during daylight and nighttime hours. Unseelie actually give off darkness when it's twilight (and this is how they know to use their glamour power).
The Unseelie court consists of nobles, from the lowliest courtier to the Dark Queen herself. They see themselves as revolutionaries and freedom fighters, although their cruelty and violence often speaks of their true nature. They have an intense hatred of the Seelie Court and it is this hatred that organizes them.