Diamond

Diamond is the sparkling, tanky warlord of the Underwater City in the Second Sea, encountered at level 1,000+. He packs 650,000 HP and his crystal-based moveset features a reflective shield passive that bounces 25% of all physical damage back to the attacker — a nasty surprise for melee mains. Drops: Diamond Necklace accessory (~5%), Crystal Shards crafting material (~15%), and solid Beli rewards. Respawn timer is 20–30 minutes in the Underwater City interior.

The reflected damage passive is Diamond's only real gimmick but it's genuinely punishing if you ignore it. Switch to a fruit exclusively — Ice Awakened or Dough Awakened deal zero reflected damage because their moves are classified as magical. Sword mains must use Observation Haki to break his guard before attacking; unguarded hits don't proc the reflection. His crystal pillar AOE has a 2-second startup — use a dash to clear the blast radius every time.

Crystal Shards at 15% drop rate makes Diamond a consistent and efficient mid-game materials farm. You'll want a stack of 30–50 Shards for crafting, and his fast respawn lets you accumulate them without excessive time investment. The Diamond Necklace at 5% is worth the hunt for the stat bonuses and trade value. Overall, Diamond is one of the most well-rounded Second Sea bosses: relevant drops, manageable mechanics, and a spawn location near fast-travel points.