I just finished the Second Magic Trial your character experiences in the story.. It's very similar to the first trial except this time there is an arch in the middle of the arena like some of the arches you'll have experienced before, where passing through an arch changes what is and is not visible, in this case stone knights. Even if they are invisible, you'll see their swords levitating and moving around and of note, they can attack you while invisible, but you can't target them if invisible.
The fighting mechanics are the same. With the boss, it's got some unblockable blast attacks (red), which must be dodged, and sometimes after a red attack, it's followed by 2 yellow (blockable) projectile attacks so anticipate them. So it's the same routine, red attack, dash, yellow attack, protecto, after ancient magic fills up, zap the boss with X, and always keep it cursed. You need to have purple, yellow, and a red attacks readily available to shoot at and explode the colored ball, it forms in his hand before launching it at you. It's much easier to explode them in his hand, than it is to dodge them.
It's tough to get images when you are fighting for your life, but I may go back to a crucial save just prior to the arena and see if I can get some good combat snaps. 🙂