Dragon's Dogma 2 Regalia Sword - Completing Dulled Steel, Cold Forge
One of the more involved sidequest chains in Dragon's Dogma 2 revolves around restoring a regalia sword of Vermund; a task you'll be entrusted with from a soldier by the name of Roman near the castle fountain in Vernworth. When you first approach the soldier below, he'll hand over the current state of the sword - in disrepair and all - and express his desire that it might be restored to its former glory. This task will require the work of a master blacksmith; and with nothing else to base your search on, it's up to the player to deduce who that might be.
Master Blacksmith Location
The Master Blacksmith you seek is Brokkr the Dwarf - who can be found in Bakbattahl. There's just one problem; he's retired, and refuses to help. His apprentice, Sara, however believes that if you can procure enough Glimmercoal to relight the forge, he might be willing to take up the hammer again to restore the regalia. Previously they gathered Glimmercoal in the Digger's Ruins just Southwest from Bakbattahl. You're told that 15 pieces will be enough; but we're going to attempt to grab 25.
Glimmercoal Location
Within the mine, you may notice that all of the ore looks the same. There is, however, a trick to prevent you from filling your packs with worthless ore; extinquish your light sources, and the Glimmercoal will grow a bright green, illuminating its surroundings. Simply explore the cave, dealing with enemies as they come, and gathering as much of the ore as needed. If you don't have 25 once you've cleared the mines, rest for a couple of days until the ore starts to respawn.
Once you've gathered 25, return to Sara and hand your haul over. Brokkr still refuses to reforge the blade himself; instead challenging his apprentice to do the deed. Hand over the regalia to her, and leave her to her devices for a while. When next you speak to her, she'll mention how she might need the use of a blazehammer - a hammer heated by being dipped directly in magma - to finish the restorations. The next day, you'll discover Sara gone - and Brokkr claiming he hasn't seen her since.
Sara's Whereabouts
Naturally, she's left to pursue a blazehammer; you can fine her at the Mountain Base Cave, on the Agamen Volcanic Island. Since this quest might spawn before players can unlock the shortcut to the Island, you may need to rush after her through the long path through Drabnir's Grotto. While we don't know for sure if this part of the quest is timed, we wouldn't test it - rush to the Mountain Base Cave as soon as possible, and you'll find her at its apex; quickly escort her back to the entrance before her hammer cools to successfully complete the quest step.
After you return to Brokkr, Sara will deliver the restored regalia sword. You can now, finally, return to Roman in Vernworth for your reward. You'll get 6000 XP and 35000 Gold for your efforts, but more importantly after a few days Sara will start offering the strongest equipment you can buy, at a 10% discount, and as one of the few sources of Dwarven style smithing. While Sara isn't the only NPC that can enhance your equipment this way, she's the only one that can do so in a convenient manner. Gautstafr is off the beaten path; meanwhile Bakbattahl is a relatively easily accessible location via oxcart. Congrats on restoring the regalia sword, and enjoy possibly the best smithy in the game!