That copper dungeon reminded me of a previous event but I can't remember what event that was hahaha. That was the event that I farmed for the two armors. But currently copper dungeon is not a good event for me because its not worth the copper that you will be getting in exchange for troop loss. All the stages have 5 corsairs each wth. Better to farm at Frosty Realm or Vulture event than Copper Dungeon.