In the boss battle against Leviathan, the part in which you are warping around from one platform to the next, I had a long period in which I was not able to hit the boss. I believe that I had to use the targeting function (R1 on the default setup for PS4) and then hit Triangle for the warp attack. So after 10 minutes of wasting potions and the like, I went out to the next stage, which was a lot more fun.