The Sanctum sex game is an adult business type of simulator existing in a strange world full of orcs, elves, and other strange creatures. Your character lives in Korthaven, a city underground which is under the rule of an evil, dark elf council hungry for all the power it can get.
One day a lovely elf called Kim come to see you. She tells you that your father is that dark elf lord and you are one of his bastards. So, suddenly you are rich and she is part of your property as your slave. The catch is you have to use that fortune to turn an existing temple into a pleasure den, which of course is known as the Sanctum.