IIRC this was turned into the new IP that Siliconera posted about a few years ago and then eventually canceled.
Source: http://www.gamespot.com/articles/the-story-behind-fortress-the-final-fantasy-game-t/1100-6431036/GameSpot said:In the years since the closure, concept art has surfaced in the online portfolios of many former Grin designers. Composer Erik Thunberg released a track for Fortress, called "Crystal Theme," on his SoundCloud page. A tech demo for Fortress surfaced along with a curious image containing a summary for a game called Valiant Saga and referencing Final Fantasy XII directly, as well as several locations from the world of Ivalice. The logos for Square Enix and Eidos Montreal were stamped on the image, suggesting that Eidos was developing its own Final Fantasy XII spin-off.
According to the summary, Valiant Saga would take place 10 years after the events of Final Fantasy XII and center around the Fortress of Faram, a stronghold in the Ivalice country of Nabradia. The Queen of Dalmasca--Ashe--hires a "lone mercenary" to vacate the Fortress's resident, an evil cult leader who wants to use the structure's ancient magics to destroy Ivalice.