The Door Hidden in the Darkness is the 279th chapter of Hiro Mashima's Fairy Tail.
With Elfman badly injured, Wendy takes his place as a member of Team Fairy Tail A. Meanwhile, Mirajane is matched against Jenny Realight, a former colleague, and the two begin a swimsuit showdown with their Transformation Magic. However, Mirajane ends up the victor as she uses Satan Soul: Sitri to defeat the Blue Pegasus Mage. Meanwhile, Arcadios meets with Datong and reveals that the Eclipse plan is complete and is only waiting for Lucy.
Summary
After his battle with Bacchus, a seriously injured Elfman is brought by the members of his team to Porlyusica. Erza, Lucy, Gray and Natsu keep praising Elfman but Elfman tells them to stop. He also tells Wendy to take his place. Porlyusica then tells the group to leave as the next match is about to begin. The group leaves, leaving the members of the Thunder God Tribe to guard him. As the group walks towards the arena, they discuss the actions of Raven Tail who have tried and failed to kidnap Lucy. Erza tells the group that they should stay vigilant and not wander around alone.
The group then arrives at the arena and sees that Mirajane is matched with Jenny Realight from Blue Pegasus. However, instead of an ordinary battle, the two Mages are having a swimsuit contest, due to both being models for Sorcerer Magazine. The two then continue to use their Transformation Magic to change swimsuits but neither side is willing to give in, prompting Chapati to say that the next set will be the last. Thinking that her victory is assured, Jenny makes a bet with Mirajane: the loser will have to appear nude in the next sorcerer magazine. Mirajane agrees and Jenny smirks, thinking that the judges will be forced to give her a higher score since they would want Mirajane to appear nude in the magazine, having not aged in the last seven years.
Jenny then transforms into her "battle form". Seeing this, Mirajane begins to transform, saying that they should finish the battle with a "clash of strength". Mirajane then emerges in her Satan Soul: Sitri form which, according to Erza, is the strongest Satan Soul. Mirajane then charges at Jenny, defeating her and earning her team ten points. Forced to follow the deal, the defeated Jenny begins to cry.
Elsewhere, Arcadios is approached by Datong, the minister of defense. Datong asks Arcadios the reason behind him wanting to kidnap Lucy. Arcadios tells him that he wanted to try a test run as he had already completed Eclipse. Arcadios then leaves, saying that he cannot be stopped. Datong asks him if he's a demon but Arcadios says that for the sake of his king and country, a man can be a demon or a god. Arcadios also says that the price of Lucy's life is cheap if it can open the gate way to changing the world.
(c)http://fairytail.wikia.com/wiki/Chapter_279