Rumiese:
Here's the plan. You weaken Istina as much as you can, while I prepare the magical Ballista. Have you seen one of those? They're rather impressive. They are powered by soulshots and can do a great deal of damage. Their main drawback is that they require a lot of energy to recharge, so please tell your team to push yourselves to collect as much magical power as you can, as quickly as possible.
That is all the advice I can give; the rest of it is up to you.
Oh, I once gave you an Energy Control Device, didn't I? You will most certainly need it for your fight with Istina, so shall I give it to you now?