Wow. The notifications only listed likes and not posts. Had to shift through three more pages of posts.
But yeah, new Wii U stage is a generic arena featured in Fire Emblem games. These arenas aren't featured in Awakening or Radiant Dawn, but are featured in the GBA Fire Emblems as well as Marth's Archanea games and (I believe) the Jugdral games as well. You send your units there to challenge randomly selected opponents of all levels and classes to farm for money and experience while risking their lives in the process. It's fun for everyone involved, don't you know. The dragon in the background is one of several opponents. As awkward as it is, in one game, manaketes were banned from arenas.
By which they meant, YOUR manaketes were banned from arenas. You could end up fighting anything short of an Earth Dragon.
Also, four days until Maybe Ridley. Hype for all.
EDIT: For final smashes I'm hoping for skin hardening.