From the Chaosium website:
An Exploration of Long-Lived Wizards from the work of Lovecraft
The works of Howard Phillips Lovecraft contain several stories about old wizards who deal in forbidden knowledge and whom seek to either extend their lifespan, to regain their youth or obtain knowledge and skills to cheat death. Some also seek to increase their knowledge by bringing back others from the dead and forcing them to answer questions.
Traditionally this form of magic is referred to as necromancy and the Call of Cthulhu rules book and Dark Ages both contain spells that deal directly with this subject. This work provides examples and revelations of these wizards in the works of Lovecraft.