How do you destroy the shadow beasts at Death Mountain?

Please help!

Oh, by the way, I searched and can't find an answer.

I'm not sure as it was a while ago I did this bit but I think the barriers are arranged in such a way that one is isolated from the other 3. If you look you'll see one doesn't really move much and you can move through gap in the barrier division to get to it. Kill that one separately then use the B attack to kill the other 3 together, making sure they're not near the barrier or you could interrupt the attack by accidentally hitting it.
Hope this helped.

If you're referring to the bit where one of the beasts is seemingly behind a barrier then

Thanks sooo much!

I'll let you know how I get on.