In Sailor Piece, players can unlock the powerful abilities of the Shadow sword by completing its Mastery quests. To begin, players must first acquire the Shadow sword from the Shadow Trainer NPC located on Dungeon Island, which requires a total of 10,000,000 Money, 15,000 Gems, and various materials. After obtaining the sword, players can interact with the Shadow Master NPC on Starter Island to begin the six Mastery quests. These quests involve dealing 1 billion damage, killing 1250 NPCs, and defeating 150 bosses, among other challenges. Players can enhance their sword's damage using enchants and passives before tackling these quests. Completing all quests grants the F move, which causes a powerful explosion, dealing significant damage to enemies and increasing the sword's overall damage by 30%. The best location for farming bosses is Shibuya Station, where players can find multiple bosses spawning every few minutes.