Attack on Titan: Before the Fall Vol 11

From the Kodansha edition

A QUEST FOR VENGEANCE Sharle has taken matters into her own hands to recruit the reclusive Angel, the original inventor of the Device that might one day help humanity fight back against the Titans. But Angel's harrowing experiences have left him scarred, and he may need extra encouragement to rejoin the struggle. Meanwhile, Kuklo remains missing, his fate in the balance... The Diamond Gem Award-winning prequel to Attack on Titan! "The dark and oppressive atmosphere sets it apart from the original series... absolutely nightmarish and terrifying." -Comic Book Resources

Source: Penguin Random House API