The Dumas Mountains are a major mountain range in southern Falmart, Special Region, running northwest to southeast, from their northernmost extent near Bellnahgo to the southern end of the range near the coast of the Blue Sea. To the southeast of Rondel, the Dumas Mountains meet the east-west trending Romalia Mountains. The mountains are traversed by the Appia Highway, connecting the cities of Italica and Sadera. Unlike the road through the Romalia Mountains, the stretch of the Appia highway seems to be passable to the modern vehicles used by the Japan Self-Defense Forces.
The mountains are traversed frequently by JSDF personnel and civilian diplomats traveling from Alnus to Sadera, including the Third Recon Team. It is possible that they are also the mountains visible from the helicopter seen after Noriko Mochizuki's liberation.
During Zorzal El Caesar's Coup, an Imperial Army dragon rider attempts to attack Special Region Resource Investigation Team 103 in the Dumas Mountains, but is killed when a dark elf- one of the Special Region auxiliaries assigned to the team- casts a fog spell, causing the rider to crash.