Farming Soul Masks in Lost Ark is an important part of the game, as they are used to upgrade your gear and progress through the content. There are a few different ways to farm Soul Masks, but the most common and efficient way is to run Chaos Dungeons.
Chaos Dungeons are instanced dungeons that can be completed solo or with a group of up to four players. They are a great way to farm Soul Masks, as they drop from all of the enemies inside. The higher the difficulty of the Chaos Dungeon, the more Soul Masks you will get. However, the higher the difficulty, the more difficult the dungeon will be.