In the Japanese and Europe International releases, many of the games bosses were made harder, and key locations were blocked off but 'dark aeons'. These were never in the US release of the game but have health from 800,000 to 80,000,000 hp. The most effective way to beat them is to get Yojimbo (from under the bridge between Calm Lands and Gagazet, and train him to use Zanmato (his overdrive, which is very rare due to the random nature of his attacks).

To beat then without using this move however needs almost perfect stats of 255 and as many final weapons and armour as possible, dodging lightening is needed to get lulu's last weapon... although 670.. a bit obsessive .. lol