The mountain range acts as a natural border dividing Crimea and other countries that surround it on the continent of Tellius. The mountains lay just inside the Crimean border and act as a defensive barrier.
The biggest incident in which the Marhaut Mountain Range is mentioned is Chapter 25 of Fire Emblem: Path of Radiance. Ike, who is then leading the Crimean army to reclaim their homeland (and who had already defeated all resistance in the country of Daein) is forced to lead his army over a mountain passage because it would take too long to go around. On the other side of the Marhaut Mountain Range from Ike's forces were members of the Gallian army, who were to join with Ike's forces. A part of the Begnion Army lead by General Zelgius also followed Ike across the mountain range.
Near the top of the particular mountain in the range that the pass crosses over, the Daein army had set a trap, although Ike already knew this but was forced to march into it. Chapter 25 is not particularly difficult, the only thing that is different is that the Daein soldiers roll boulders down the mountain at the player's forces. Also, all units mounted on horseback have greatly decreased movement.