Question: Who developed the game which Folkenstal features weapons and armors in a cosplay? 

Context articles: Prince of Persia: Warrior Within
Alliance: The Silent War
Folkenstal
The Elder Scrolls Online
Long War (mod)
Transformers: Dark of the Moon (video game)
Dementium II
Halo 2
List of Homestuck characters
R.I.P.D. The Game

Prince of Persia: Warrior Within is an action-adventure video game and sequel to "".
 "Warrior Within" was developed and published by Ubisoft, and released on December 2, 2004 for the Xbox, PlayStation 2, GameCube, and Microsoft Windows.
 It picks up where "The Sands of Time" left off, adding new features, specifically, options in combat.
 The Prince has the ability to wield two weapons at a time as well as the ability to steal his enemies' weapons and throw them.
 The Prince's repertoire of combat moves has been expanded into varying strings that allow players to attack enemies with more complexity than was possible in the previous game.
 "Warrior Within" has a darker tone than its predecessor adding in the ability for the Prince to dispatch his enemies with various gory finishing moves.
 In addition to the rewind, slow-down, and speed-up powers from "Sands of Time", the Prince also has a new sand power: a circular "wave" of sand that knocks down all surrounding enemies as well as damaging them.
Alliance: The Silent War is a first-person shooter video game for Microsoft Windows being developed by Windward Mark Interactive to simulate combat over 90 years of human history, taking the player from World War I to modern day.
 The player will have access to 200 real world weapons using an innovative system called the War Studio.
 With it, gamers can search for firearms from a number of different parameters, such as caliber, country of origin, and year of production, create multiplayer matches in which weapons from different time periods can be used by each team, or give different types of units weapons that would not normally be used.
 Players will also have the ability to adjust the amount of realism as a part of their settings.
 The game will run on the Alliance Engine.
Folkenstal from Switzerland, a Cosplay artist, highlighting the weapons and armors from the latest MMORPG, The Elder Scrolls Online.
The Elder Scrolls Online is a massively multiplayer online role-playing (MMORPG) video game developed by ZeniMax Online Studios and published by Bethesda Softworks.
 It was originally released for Microsoft Windows and OS X in April 2014.
 It is a part of "The Elder Scrolls" series, of which it is the first multiplayer installment.
Long War is a fan-made partial conversion mod for the turn-based tactics video game "" and its expansion, "".
 It was first released in early 2013, and it exited beta at the end of 2015.
 Almost every aspect of the original game is altered, creating a longer, more complex campaign that presents players with more strategic choices and customization options.
 "Long War" adds a significant number of new soldier classes, abilities, weapons, armors, and usable items, and also introduces new features, including soldier fatigue and improvements to alien units over the course of the game.
Transformers: Dark of the Moon (marketed as Transformers: Dark of the Moon - Stealth Force Edition for Nintendo 3DS and Wii) is an action-adventure video game which was released on June 14, 2011 in North America.
 The Wii and the 3DS versions were very different to the Xbox 360 and PS3; there was also a DS version that was also different to the console and wii and 3DS versions.
 "Transformers: Dark of the Moon" was revealed on February 12, 2011 along the release of the trailer for the game.
 The PlayStation 3 and Xbox 360 versions of the game were developed by High Moon Studios who previously developed "" while the Wii, Nintendo DS, and Nintendo 3DS versions were developed by Behaviour Interactive.
 The game features a mode known as "Stealth Force" in which characters only partially transform from their vehicle mode.
 Weapons protrude from the vehicle form and more precise controls are available, such as strafing, airplanes also use this Stealth Force.
 Electronic Arts released mobile incarnations of the game for Symbian, iOS and BlackBerry.
Dementium II is a first person, survival horror video game developed for the Nintendo DS.
 It is the sequel to 2007's "", also for the Nintendo DS.
 The game was developed by Renegade Kid and published by SouthPeak Games.
 It was released in 2010 and features many improvements over its predecessor "", including different weapons, a larger variety of enemies, the ability to jump and crouch, save points, more environments, an improved map system and the removal of respawning enemies.
 Weapons include shank, revolver, sledge hammer, shotgun, assault rifle, dynamite, flame thrower, nail gun, and relic.
 Items include flashlight, ammo for any of the weapons, adrenaline shots, pills, and medkits.
 A remastered version of the game was released for Microsoft Windows and Mac OS X on December 17, 2013.
Halo 2 is a 2004 first-person shooter video game developed by Bungie Studios.
 Released for the Xbox video game console on November 9, 2004, the game is the second installment in the "Halo" franchise and the sequel to 2001's critically acclaimed "".
 A Microsoft Windows version of the game was released on May 31, 2007, developed by an internal team at Microsoft Game Studios known as Hired Gun.
 The game features a new game engine, as well as using the Havok physics engine; added weapons and vehicles, and new multiplayer maps.
 The player alternately assumes the roles of the human Master Chief and the alien Arbiter in a 26th-century conflict between the human United Nations Space Command and genocidal Covenant.
"Homestuck" is a webcomic written, illustrated and animated by Andrew Hussie as part of MS Paint Adventures.
 The series centers on a group of teenagers who unwittingly bring about the end of the world through the installation of a beta copy of an upcoming computer game.
 "Homestuck" features a complex story and a large cast of characters, starring the four children John Egbert, Rose Lalonde, Dave Strider, and Jade Harley.
 Hussie invented an alien species, called trolls, that have a unique culture.
 "Homestuck" characters are particularly popular at anime conventions to cosplay.
R.I.P.D.
 The Game is a co-op third-person shooter video game developed by Saber Interactive and published by Atlus USA.
 It was released on July 17, 2013 for the Xbox 360, PlayStation 3 and Microsoft Windows.
 The game is primarily a survival mode, and is based on the film "R.I.P.D.".
 The gameplay is derived from Old School Game's previous game, "God Mode".
 Players in "R.I.P.D.
 The Game" are able to play as Roy Pulsipher or Nick Walker in a cooperative horde mode gametype against renegade ghosts also known as "deadoes", who stay on earth to avoid their fate in the afterlife.
 Matches are composed of five rounds with each round increasing in difficulty compared to the last.
 Players are able to buy and upgrade weapons using in game currency.
 These weapons include a standard arsenal of shotguns, assault rifles, and references to the movie such as a banana or a hairdryer.
 Enemies can be defeated through in game firearms or by standing next to marked enemies in order to arrest them.