How to beat Rellana, Twin Moon Knight - Boss fight NG+4 - ELDEN RING Shadow of the Erdtree DLC [4K]

"Born into the Carian Royal Family, Rellana is the younger sister of Rennala, who gifted her lustrous black hair. In her childhood, she and her elder sister met the twin moon, which were overlapping, as though nestled against one another. Rellana also had a sole entry into ritual combat-a demonstration of fidelity to the Erdtree.
At some point, Count Ymir instructed Rellana in the sorcerous arts, though he later abandoned his allegiance to the moon. In a similar fashion, she later disavowed her birthright and chose to stand at Messmer's side instead, knowing full well that not even the brilliance of the moon could grant him succor. Before long, she became known as the Sword of Messmer.
During the search for Miquella, a Tarnished warrior fought through Castle Ensis and engaged in combat with Rellana, defeating her and opening a path to the Shadow Keep."