Honkai Impact: Kiana Saves the World, Find Durandal?

"I... Deceived her." In the silent, cold space, the boy's voice carried a barely perceptible bitterness. ["Ding, quest issued: Find the savior—Kiana Kaslana, and assist her in saving the world. Reward: Determined based on quest progress. Failure: Participation below 50%, this world will perish."] "I approached her, solely for the quest—to assist the girl named Kiana Kaslana in saving the world." [The girl awoke with a start from the biting cold, her mind blank except for the vast snowfield. Her long golden hair slipped down her temples, and through the gaps in the strands, she...]