Maybe could get renamed to Gargoyle Fort, because it isn't much of a big castle...but anyways - a small battle arena where stage knock-outs can happen quickly, while at the same time providing a layout where strategy practice and lobbing your Gachaboms at the best timing possible will be required to best the Staff Ghosts in the Prison Break mode.
The name and idea of the stage are based off Killer Instinct 2, specifically Gargos's stage...hence not only it is named Gargoyle Castle, but also uses that game's stage music as well.
A stage meant to be set somewhere in San Francisco - location that inspired City Escape from Sonic Adventure 2 [and uses a song from Street Fighter III to vary].
It is a large symmertrical stage with a wide open area on the center, some ramps on the sides and the edges of the map having roofs plus a ramp to get on top of those. Giving chase in low player count battles may be tough, but you should always have someone locked in due to the central layout if there's a whole crowd playing at once.