In this map, the dragon veins are located in front of the statues which will allow you to either open a path or flood the area with lava. There are also ranged enemies here called Stoneborns, who can lob boulders at a maximum range of 5 spaces. Flying units can traverse the flaming chasms and mountains so use them to your advantage.
In the first statue, the LEFT vein will create a path. The swordmaster across the first chasm drops a Venge Katana. In the second statue, the RIGHT vein will create the bridge. In the third statue, the RIGHT vein will create the path. The stoneborn in the third area has a Master Seal in its inventory.
Keep pushing forward and heal in between. Remember to check the enemies' attack range after creating the path; keep an eye out for the bow-wielders so you can avoid placing your fliers in their attack range. As soon as you get near the boss stoneborn, the terrain will change to lava and reinforcements will surround you on both sides.
Lava will damage all your units at the start of each turn, heal the invaders, and will restrict the movements of your ground forces. Fliers can still be damaged but will not be affected by the movement restriction. Two batches of reinforcements will continue appearing in the lava terrain at this point. It's up to you if you want to finish the battle quickly or stand your ground and wipe out all enemies. Defeating the two stoneborns will make them drop another Master Seal and an Arms Scroll.
After upgrading any of your Castle's puppets to LV3 and after completing a battle, Yukimura will arrive in your castle as an additional ally.