I have absolutely no idea what the giant creatures you have to fight in this area are. I started playing Dungeons & Dragons when I was like, five, and I have never seen these things in any other material. They look like some sort of basilisk-type dinosaur? Most annoying about them is that they have wonky hitboxes and somehow hit you while they walk. The best way to deal with them is to lure them out one by one and wail on them as hard as you can while they come out of the ground. You can also wack them a bunch while they burrow again. Ironically, the giant one outside of the temple itself is actually easier than the smaller ones, primarily because you can throw him in the spin cycle.
The sunken temple is kind of a weird area because of how easy it is. The minotaur's are so slow moving that, after they charge at you, they really can't ever catch up to you. They can hurt if they manage to land a blow. Either way, after the area leading up to it, it's hardly an inconvenience.
Oh? Story? Yeah, no. Something about a water stair and magical magic that brings you to the final area of the game. Buckle up.