Eternal War.

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We fought over a girl on a walking battleship. Demons won.

We fought over magical treasure in a sea. Angels won. Machina got back the girl from the first fight.

We fought over the same magical treasure in a volcano. Machina got most of it thanks to girl from first battle, Demons got a bit and a powerful fighter stolen from Machina (Krieg), Angels exploded.

That about sums the main points up.
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