The open area is a crevice with many sniping areas up above with battlements on the sides as well where one could hitch a ride on the Shen Gaoren if one dared.
The arrow is blocked by the rampage of the claws.
Grantz notices the arrow that flew.
Archer! Wherever you are! You won't be able to hit its face until you bring it down! You need to hurt all its four legs to bring it down.
Grantz continues to dodge the onslaught of claws while his demons attacked the back left leg.