Since Diether is using a thicker sword, his overhead strike carries more strength.
Aside from that, his Solar Sword has a natural fire affinity which can cause trouble to the Dark Elves.
Boom!
Diether poured a lot of his Spiritual Energy into that strike. It is a very simple strike but if it managed to successfully hit the target, it wouldn't matter whether they are First-Class Arcanist or Fourth-Class Arcanist. That strike can't be easily defended by one's physical body!
Clack!
"Tsk! What's that?"
Diether's movement was extremely fast since he used his Flash Step to appear behind the huge Dark Elf. He wanted to cut him from the back but instead of hitting the Dark Elf's body, he hit something sturdy but it doesn't seem to be made of metal.
He then saw black energy forming at the spot where he hit the sword.
"Gahaha!" The huge Dark Elf laughed seeing how ineffective his attack was.