The Shadow Sorcerer: A Sorcerer Subclass

From the introduction: The shadowfell is a realm of mind-shattering magical power. It twists and distorts itself without rhyme or reason except to drive its denizens ever deeper into madness and despair. Sometimes, the power of the Shadowfell can bleed through to the material realm and seep into the very fabric of an individual granting them a measure of power.