For where such knights are, there Camelot is. And so Camelot endures! 
Demon Knights #12 is an issue of the series Demon Knights (Volume 1) with a cover date of October, 2012. It was published on August 8, 2012.
Synopsis for "The Avalon Trap"
The Demon Knights make their way into Morgaine le Fey's tower, which is made up of impossible architecture. Le Fey aims to keep the knights distracted by means of magic while her plans unfurl. While exploring, Madame Xanadu and company find a sacrificial mockery of the Round Table and among the sacrifices is the corpse of Xanadu's sister, Tui. When the group realizes the magic in the air is sapping their strength, they are attacked by various beasts.
While fighting, the group is gassed and all pass out. When they awake they find themselves restrained in the shape of a magical seal. Morgaine le Fey reveals her plan to her siblings Arthur and Xanadu and the rest of the Demon Knights - to transfer her consciousness into the body of Merlin. The tower, she explains, was built to lure Merlin back and to destroy his mind. Furthermore, she plans to sap the life force out of the knights to make Merlin's body even stronger.
Before exiting, Morgaine le Fey tells Xanadu that she regrets having had to kill their sister, Tui, but that she will be a good person as Merlin. By repeatedly transforming, Etrigan breaks his bonds with hellfire. He releases his companions and they all attack Morgaine le Fey who in retaliation attempts to possess the body of Xanadu. Arthur intervenes and Morgaine le Fey and Arthur fight for control over his body. Arthur, realizing he is losing control, uses all of his strength to destroy the source of the dark magic in the tower - sacrificing himself and destroying the tower in the process.
Upon exiting the ruins of the tower, the Demon Knights with Merlin's body in tow search for the way to Avalon. When Xanadu realizes the way is gone due to Morgaine le Fey's desecration of the land, Etrigan betrays the group and brings them all with him into Hell.
Appearing in "The Avalon Trap"
Featured Characters:
- Demon Knights
- Al Jabr (Dies)
- Etrigan (Jason Blood)
- Exoristos (Dies)
- Horsewoman (Dies)
- Madame Xanadu (Dies)
- Shining Knight (Ystin) (Dies)
- Vandal Savage (Dies)
Supporting Characters:
- King Arthur (Apparent Death)
- Breaker the Horse
- Vanguard the Flying Horse
Antagonists:
- Morgaine le Fey (First full appearance) (Apparent Death)
- Mutated animals (All die)
Other Characters:
- Knights of the Round Table (Only as corpses)
- Merlin (Appears only as a corpse)
- Tui (Real name revealed) (Appears only as a corpse)
- Demons (Mentioned only)
- Gods of Olympus (Mentioned only)
- Nimue's sisters (Mentioned only)
Locations:
- Prime Earth
- Sphere of the Gods (Unnamed)
- Hell (Cameo)
- The Dreaming (Unnamed)
- Faerie (Unnamed)
- Avalon (Mentioned only)
- Faerie (Unnamed)
Items:
Concepts:
- Magic
- Middle Ages
- The Red (Behind the scenes)
Trivia
- Tui is one of the Ladies of the Lake.