A derangement is a specific form of mental illness or insanity. In the Storytelling System, derangements are often a consequence of the loss of Morality or of actions committed contrary to the character's Virtue. Similarly, in Vampire: The Masquerade, derangements can be caused by the loss of Humanity via degeneration. In both settings, certain supernatural abilities, such as the Dementation Discipline of the Malkavians, can also cause temporary or permanent derangements.
Many Derangements can be taken as Flaws during character creation. In the Storytelling System, a derangement is classified as either mild or severe, and grants bonus experience accordingly like other flaws. In the Storyteller System, each derangement may be represented by its own distinct Flaw, though in some books they are instead generally covered by the Flaw "Deranged".
Dice pool to resist gaining derangement is character's morality after loss.