The Ash of War imparts Fire affinity to an armament and introduces the skill "Eruption."

This skill, utilized by the knights who serve at Volcano Manor, involves slamming the armament into the ground, spawning roiling lava which spouts up upon release.

Usable on large and colossal swords, axes, and hammers.

To obtain these Ashes of War, visit the Volcanic Mansion in Gemmel Volcano.

The Ashes can be acquired by completing side quests.

Initiate the process by speaking to Tanis, the hostess of the mansion, to obtain the room key.

Open the door of the restaurant using the key, find a letter from the volcano mansion on the dining table, and then head to the north of the ruined house of the warriors of Ningmgfu to defeat the ancient knight Ishutuo.

Return to the restaurant of the volcano mansion and talk to Bernal to obtain the Battle Ash for 8000 runes.