Seems like they're preparing a new part of Time Temple.

That door can actually lead to the past. See the red, burnt Leafre background?


This is the background that looks like it. But why is it together with Time Temple?

Maybe, it's because the door leads to the past. The past of Heroes. The past Leafre map, was the place where Aran and Freud were defeated by the Black Mage, and as shown in the Mercedes trailer, there was a previous battle of Mercedes agains't the Black Mage, inside a very dark Time Temple map, she loses, and faints.
This could mean this area is related to the day where the Black Mage was sealed, and the Heroes defeated.

By looking at the trailers, Mercedes and Freud fought the Black Mage inside it's throne room, in the Temple. Aran was injured, late, and busy taking care of rescuing the kids with Athena.
Mercedes is defeated, Freud survives, and the Black Mage goes after Aran in that Leafre themed map. Both Aran and Freud are defeated.

Aran, Mercedes, Afriend and Freud are cursed.

*Aran was the first one to be defeated, he was frozen already in the place where the Battle took place.

*Afrien, heavily injured, can't move and begins to freeze, he lays an egg, and begs Freud to hide that egg, so the Onyx Dragons won't be extinct, and wait for the egg to find it's rightful owner, a man as pure of heart as Freud. He hides the egg, and dies. Since he was just an ordinary human with a pure heart.

*Mercedes wakes up, and goes to the Past Leafre area, she finds Afrien freezing, and Freud dead. She cries for both, and then remembers of Eurel, Afrien using his last powers, teleports to her city to try to save her, and everything was freezing there too. She goes after the citizens, and fulfills their last wishes. She, at the last quest, is asked to close the town, maybe for the Black Mage to stop thinking about destroying it.
She closes the door entrances with a heavy amount of magic from the three sages, after it, everyone's frozen, and she finds herself alone. Not being able to help her friends, and finding everything destroyed, she goes to her room and is frozen in a very long sleep.



This area looks like you'll be coming back in past, the day where the Great Battle occured. Since it looks like there were two battles agains't the Black Mage, one in it's habitat, the Dark Time Temple part, and the one in the burning forest, that after his last spell, turned out to be Rien. Aran was frozen in the place where the Battle took place, and Afrien too, that's why they're in Rien.

Really, looking forward to this. :O

Seems like that after Demon Slayers, the Black Wings are actually showing up, and there's a symbol for them, the symbol in Akyrum's head, an eye, also is shown when Black Wings attack Magatia.



Also, this is the cat form that the guy in the beginning of the Demon Slayers tutorial is sealed into. He REALLY looks like the cat in Sailor Moon. :O