Can't use brackets in YAML.

src/main/java/com/gmail/nossr50/config/AdvancedConfig.java

@@ -286,7 +286,7 @@ public class AdvancedConfig extends AutoUpdateConfigLoader {
     public int getKrakenTriesBeforeRelease() { return config.getInt("Kraken.Tries_Before_Release", 50); }
     public int getKrakenHealth() { return config.getInt("Kraken.Health", 50); }
     public String getKrakenName() { return config.getString("Kraken.Name", "The Kraken"); }
-    public String getServerUnleashMessage() { return config.getString("Kraken.Unleashed_Message.Server", "[PLAYER] has unleashed the kraken!"); }
+    public String getServerUnleashMessage() { return config.getString("Kraken.Unleashed_Message.Server", "(PLAYER) has unleashed the kraken!"); }
     public String getPlayerUnleashMessage() { return config.getString("Kraken.Unleashed_Message.Player", "THE KRAKEN HAS BEEN UNLEASHED!"); }
     public int getKrakenAttackInterval() { return config.getInt("Kraken.Attack_Interval_Seconds", 1); }
     public int getKrakenAttackDamage() { return config.getInt("Kraken.Attack_Damage", 1); }

src/main/java/com/gmail/nossr50/skills/fishing/FishingManager.java

@@ -91,7 +91,7 @@ public class FishingManager extends SkillManager {
         world.strikeLightningEffect(location);
         player.sendMessage(AdvancedConfig.getInstance().getPlayerUnleashMessage());
         world.playSound(location, Sound.GHAST_SCREAM, Misc.GHAST_VOLUME, Misc.getGhastPitch());
-        mcMMO.p.getServer().broadcastMessage(AdvancedConfig.getInstance().getServerUnleashMessage().replace("[PLAYER]", player.getDisplayName() + ChatColor.RED));
+        mcMMO.p.getServer().broadcastMessage(AdvancedConfig.getInstance().getServerUnleashMessage().replace("(PLAYER)", player.getDisplayName() + ChatColor.RED));
 
         Squid kraken = (Squid) world.spawnEntity(player.getEyeLocation(), EntityType.SQUID);
         kraken.setCustomName(AdvancedConfig.getInstance().getKrakenName());

src/main/resources/advanced.yml

@@ -423,5 +423,5 @@ Kraken:
     Attack_Interval_Seconds: 1
     Attack_Damage: 1
     Unleashed_Message:
-        Server: [PLAYER] has unleashed the kraken!
+        Server: (PLAYER) has unleashed the kraken!
         Player: THE KRAKEN HAS BEEN UNLEASHED!