From Lost Odyssey Wiki
Boss Strategy
This is an interesting battle, but not a particularly difficult one. The battle will start off one with three Mantas on the enemy's front row, and a Mantalas in the back. None of them have too strong of an attack: they'll probably hit between 100 and 150 damage each. How they act in battle is the noteworthy thing, though. If you do any damage to the Mantalas he'll use Bizarre Howl, calling whatever number of Mantas are necessary to make three (three if there are zero, two if there are one, one if there are two), then he'll hop over the side of the ship. He won't reappear until the Mantas are disposed of.
Because he employs this tactic you'll want to make sure every hit counts. To do this, at the start of the battle take out the three Manta's first, to reduce the enemy GC to zero. Then, try and land a Grounda on the Mantalas; it should do over 1,000 damage to him. Once the new Mantas are out, you'll have to be careful when selecting your actions you don't want to waste your one strike at the Mantalas with something weak. A tactic that works is to have Seth and Kaim both attack the first Manta, then select Grounda with Jansen, Cooke and Sarah (it won't matter what target you select.) In effect, Kaim and Seth will act first taking down the first Manta, two of the mages will take down the second and third Mantas, and then the Mantalas will use Appear only to be hit by the third Grounda. If you're using Mack instead of Cooke, it's not a problem. Just have him cast Minda on Sarah or Jansen on his turn or something. The difference is that you won't hit the Mantalas on the same turn he appears, but you can have Seth, Kaim, Mack and Jansen use Defend and just let Sarah blast him with it on the next turn. The battle, by design, will take a handful of turns, but it's not difficult if you plan your attacks.
Information from German Dragon's FAQ/Walkthrough
