Glimmer in the Umbral Dark

Glimmer in the Umbral Dark (晦冥の眩耀) is the 4th and final chapter of the 17th and final volume and the 64th chapter overall of the Attack on Titan: Before the Fall manga, written by Ryō Suzukaze and illustrated by Satoshi Shiki.

Overview
Xavi and Kuklo trade blows and Xavi reveals the root of his hatred of the Titan's Son; he also mentions a secret about Sharle that stuns Kuklo. Their duel is interrupted by the arrival of Ogre and Kuklo must now fight for his life against the Titan that killed his parents. At the camp, Rosa and team ten combat a five meter Titan and are overcome with horror when Ogre appears near their camp as well.

Summary
Xavi lunges at Kuklo and they cross swords while flying throughout the trees. Affirming again how he will kill Kuklo, Xavi mentions how Sharle would immediately suspect him if Kuklo died within the Walls and, due to not wanting to lose the last surviving member of his family, waited for the right time to strike. He mocks Kuklo's lack of knowledge regarding human emotions and bitterly states that Sharle loves him; Kuklo is taken back by this and Xavi strikes once again, revealing his deep rooted hatred of Kuklo stems from how he never fought back against Xavi as a youth. When Kuklo responds that he had no choice and would have died if he did, Xavi affirms this but still views it as a curse upon his life. Vowing to eradicate this curse once and for all, he charges Kuklo again.

As the two continue to fight, a loud crash is heard and they both spot Ogre, the ten meter Titan, appear nearby and then peers down at them. As the Titan reaches out to grab them both, Kuklo shoves Xavi out of the way and is caught in Ogre's grasp. Xavi flies away, pleased that Kuklo sacrificed himself and will be certainly crushed by the Titan; however, he stops on a tree branch and glares back at Ogre as it begins to crush Kuklo.

Back at the camp, Rosa charges the five meter Titan that seemingly has crushed the tent where Felix was resting. Cardina tries in vain to stop her and as Rosa flies towards the Titan, she is struck by the body of a deceased Survey Corps soldier. Falling towards the Titan's mouth, Rosa is saved due to Carlo and one of the vice captains striking the Titan in the leg. Ivo tells Rosa they need to regroup but both are stunned and horrified to see Ogre nearby; Rosa spots two blades sticking out of its fist and realizes Kuklo is caught in its hand.

Struggling to get free, Kuklo recognizes the Titan trying to crush him as the same one that killed both his mother and father years ago. Remembering his vow to Sharle to fight the Titans for the sake of a better tomorrow, Kuklo raises his blades and swears he will defeat it.