Runemals

The Mountain History chapter can be found at the yellow flag (middle right of the map). You need to have finished the Volcano history chapter (first quest at the red flag) before this one unlocks. Before you are eligible to play this you need to have one Runemal of level 30 or higher. Once you meet the requirements go to the yellow flag (middle right side) on the map and win the battle.

Having a full team (six Runemals) and having Runemals of a higher level will help you complete this mission.