Trails of Cold Steel: the Erebonia arc, in four parts
The Erebonia arc moves the saga inside the militaristic empire that Liberl and Crossbell had only seen from outside. It follows Rean Schwarzer and the experimental Class VII of Thors Military Academy, nobility and commoners deliberately mixed, through four games with a clean two-act structure. Cold Steel I (2013, PS3/Vita) is a school story that keeps glancing at the empire's class war; Cold Steel II (2014) begins weeks after the first game's ending, in the civil war that ending ignited. Then a hinge: Cold Steel III (2017, PS4) jumps forward, making Rean an instructor of a new Class VII at a branch campus, and widens the lens to the whole continent, it is the first game that demands the player know Sky and Crossbell. Cold Steel IV: The End of Saga (2018) closed the arc with, at the time, the largest playable cast in the series.
The arc's production history tracks the series' Western growth. XSEED localised I and II (December 2015, September 2016) with full English voice acting; the PC port of the first game added nearly 5,000 newly voiced lines. From III, English publishing passed to NIS America. Falcom built I–IV on Sony's PhyreEngine rather than its in-house tools, a choice president Kondo later cited when Falcom returned to a proprietary engine for what followed. And the arc's end was always mapped: Falcom has said the saga's overall endpoint was decided around the time of Trails in the Sky, and that by IV's close the full story stood at over 60% complete. The capstone that ties Erebonia to Crossbell is Trails into Reverie.