Pirotesse (Legend of Crystania)

[K.I.L.E.R]

Why is she called Sheru AND Pirotesse?
Weird.

Can someone explain to me the whole story. It's too complex.
So far I got these things:

Some guys come into Island.
Island falls apart.
Ashram is taken over by devil.
Ashram kills everyone.
Ashram is restored.

WTF???