To unlock the series of quests from Min-Sun that help craft Black Steel Armor, you must complete the blacksmith floor in the Demon Tower at least once and additionally be at least character level 71.

The next step is activating the "Favor" quest, which involves obtaining three ancient items:

• Artisans' Chronicle - an ancient book that can be obtained from the armorsmith in the Demon Tower on the sixth floor.
• Red Forest Root - located at the end of the Red Forest.
• Flame of the Damned - to obtain it, you must travel to the Fire Land, where you can find two mini-bosses from which the artifact can drop.

After collecting all items, the possibility of crafting Black Steel Armor is enabled. To craft it, you need 2x Black Steel, which can be obtained in the Land of Giants from Thousand Fighters and Chests, and Devil's Horns, which can be dropped from the Death Reaper, found on the last floor of the Demon Tower.