In Sailor Piece, players face off against Shadow Soldiers, powerful enemies that spawn in the Double Dungeon. These foes are characterized by their black horned helmets, dark armor, and distinctive blue skin. To access the Double Dungeon, players must collect all Dungeon Pieces and speak to the Dungeon Master on Dungeon Island. A Dungeon Key is required to summon a portal, allowing up to four players to enter and select the dungeon's difficulty. Shadow Soldiers have a very low spawn rate, but this increases significantly when playing on Extreme difficulty. Defeating these enemies yields valuable rewards, including Gems, Money, and Legendary chests, which can contain Clan Rerolls and evolution items. Notably, players need to defeat 25 Shadow Soldiers to complete the Shadow Monarch Mastery questline, although this can be achieved over multiple dungeon runs. With their high damage output, players should ensure their characters are well-equipped before engaging these formidable foes.