- "You will be asked a question. Answer thusly: "Sanguine, my Brother." You will gain entrance to the Sanctuary. Once inside, speak with Ocheeva."
- ―Lucien Lachance
The Black Door, also known as Black Doors, serve as entrances to the Dark Brotherhood Sanctuaries across Tamriel. They are guarded by different verbal passcodes in the form of riddles.
- The Black Door in Cheydinhal asks, "What is the color of night?" with the answer being: "Sanguine, my brother." The correct answer does not become available until the Hero of Kvatch completes their first contract for Lucien Lachance.
- The Black Door in Falkreath asks, "What is the music of life?" with the correct answer being: "Silence, my brother." Answering incorrectly results in the door replying, "You are not worthy." The correct response is not an option until the Dragonborn learns it during either the quests "Destroy the Dark Brotherhood!" or "With Friends Like These...."
- The Black Door in Dawnstar asks, "What is life's greatest illusion?", to which the correct answer is: "Innocence, my brother." learned during the quest "The Cure for Madness."
- The Black Door in the Gold Coast asks, "What is the flavor of fear?" to which the correct answer is: "Sublime, my Brother."
- The Black Door in the Blackwood Borderlands asks, "What is the gift of death?" to which the answer is: "Solace, my Brother." It grants access to the Xith-Izkul Sanctuary, but is only opened by Green-Venom-Tongue during "A Ghost from the Past."
- The Black Door emits a faint, heavy and slow breathing noise as well as deep, heavy heartbeats.
- The Black Door dialogue cannot be skipped, much like a conversation with a Daedric prince.