Grimmauld tér 12. (or Grimmauld Place 12, in english) is a hungarian non-profit Harry Potter cosplay group/club.

History:
It was created by Viola Madarász in early 2012(March,22 to be exact but the idea came earlier, around late 2011), when she and a few of her freshly-new HP friends joined together to take part at a convention called "MondoCon" at Budapest. They were only cosplaying a few characters such as Bellatrix Lestrange,Narcissa Malfoy,Severus Snape(later Andromeda Tonks) and Hermione Granger. Soon after that the first ever photoshoot of the group were happening in June, when another character joined the club, who was none other than Luna Lovegood. After that came the idea to finally get a proper name for the club that both represents the good and the dark side. Grimmauld tér 12 became the right name and the group was on the way to get more and more people involved. Since mid-summer of 2012 (when the organisation of the group's first event started - Harry Potter Halloween) more characters joined the club, including Lord Voldemort, Severus Snape, and Sirius Black.
The group attended several conventions since forming. In May 18, 2013 they took part in HoldfenyCon's cosplay performance competition which was prevented by months of preparing and crafting. However they did not win even though it was a success for the "audience".
In late 2012, the pre-production and castings started for the group's first-ever planned webseries, titled as "Mudblood." Shootings began in mid-2013 with scenes of the first and the fourth episode.
The first episode ("The Escape") was completed and debuted on Youtube, December 1, 2013. However due to many problems, the result was not what people expected.

In August 31, 2013, the group hosted their first ever (free) convention for hungarian Harry Potter fans, aka Pottercon, which was the most successful event since their forming.
By the new year 2014, they started thinking about new ideas, to make the group better and more well-organized.
In March 3rd, a new video titled as "The Duel" was debuted on Youtube, in honor of the hungarian PotterPride day. It's a HP themed silent film, featuring Gryffindor and Slytherin students.
The video itself was a success, and it's still getting many views on Youtube.
This silent film is the beginning of their video/film-making career, and by this time, the group is focused on the pre-production of their newest video.

See the list of the current members here.