The Hollow Marks allowed monsters to assume a battle form, granting them new power and abilities.
It wasn't an all-powerful ability, but without the Hollow Mark, Sarka would never have been able to wound the Dark Knight so severely. She wouldn't have been able to take a single step forward in the power level she needed to do so under any other circumstances.
Perhaps only monsters like Vyora, who possessed devastating trump cards, could have achieved a similar effect, but that was unlikely to happen considering that even her attack under the Hollow Mark couldn't seriously wound the Dark Knight.
But the Dark Knight himself didn't have a Hollow Mark - his sword did.
And now, his sword had activated its Hollow Mark by the Dark Knight's will.
Tremble. Tremble. Tremble.
A powerful surge of amber energy burst forth, accompanied by violent gusts of wind.
