By opening all of the others.
behind the oakfield demon door.
kick a chickin in it's mouth
the hammerthyst can be found in the homestead demon door, which can be opened by preposing or blowing a kiss to someone in front of the demon door. It is found in the windmill
It is closest to the water. You have to blow kiss someone. :)
With a key my friend
You get in the demon door behind the Bordello in the Dark woods. To get through the door you have to sleep with 10 people.
It reveals why he has died
You have to hold it until he tells you to end with style. The he will open. :)
Behind the demon door in wraithmarsh just behind the house in the cave.
To open the demon door in Rosa Cottage in Fable: The Lost Chapters, you need to perform an act of great evil. The demon door will open once you have sacrificed a large amount of moral standing, such as sacrificing multiple villagers or eating several crunchy chicks.
To open the Bower Lake Demon door in Fable 2, you must respond to the script it gives with expressions. The expressions needed are: blood-lust roar, fart, middle finger, worship, blow kiss, growl, point & laugh, laugh, and vulgar thrust. Your reward is the Lucky Charm Augment and one less Demon Door you have to open to be able to open the Demon Door under the Fairfax Castle.
To open the black door in "Castlevania: Dawn of Sorrow," you need to acquire the "Demon's Fang" ability. This is obtained by defeating the boss, Celia, in the game's final area. Once you have the Demon's Fang, return to the black door and use the ability to unlock it, granting you access to new areas and challenges.