At Tunnel's End, Light

Talk to Yelan. After exiting the Domain, Yelan finds the final Note of Unknown Origin, left by her ancestor Boyang. It details how two brothers received the Fantastic Compass and went to The Chasm during the war in Khaenri’ah. Only one returned, having lost his sanity, possibly due to Bosacius' karma as they lacked Visions. Boyang apparently never found a way out and died with Bosacius. Paimon accidentally knocks the Fantastic Compass, causing it to light up when Yelan and Xiao reach for it simultaneously, giving Yanfei an idea.

Yanfei theorizes she can use the compass by conjuring memories. She recalls a book stating an adeptus made a device to seal evil monsters and gave it to a human friend. They later used it together to exorcise demons, proving mortals and adepti can coexist. Yanfei, having both adeptus and human blood, attempts to power the compass, but it only slightly activates, suggesting her power isn't enough. She suggests returning to Kuki and Itto with a new plan.

Go back and meet up with the ones left behind. Follow the tunnel east and return to the camp. Talk to Kuki to trigger a scene. Yelan expresses defeat, but Yanfei explains her idea: the compass needs the combined power of an adeptus and a human, not necessarily from one person. She proposes Xiao (adeptus) and Yelan (human with magic arts training) combine their power. They agree to rest before trying.

After resting, Yelan chants a spell onto the compass while Xiao pours in his adeptus energy. The compass amplifies this, shooting a beam into the air. Yanfei realizes it's an amplifier. Xiao states he will maintain the energy level. Yelan steps back, and Xiao increases the power. The compass creates a floor that lifts them. Dark shadows attack, trying to keep them there. Yelan fights them off. Xiao's power wanes, but he exerts more effort, recalling Zhongli warning him of The Chasm's dangers.

Xiao's mask begins to crack under the strain. The rest of the group helps Yelan fight the shadows, but the floor cracks, and Xiao's mask shatters. Just as all seems lost, Xiao transports the group out, sacrificing his remaining power. The compass floor shatters, and Xiao falls. A mysterious power intervenes and transports him out with the others.

All end up topside. Yanfei is relieved Xiao is safe. Yelan thanks Xiao for saving them, but decides against expressing deeper feelings. Xiao states he couldn't have done it alone, and you thank Yelan. Yelan suggests everyone rest and offers to scout. After Yelan leaves, Yanfei tells you that Yelan feels she didn't contribute much and believes Xiao saved everyone, giving up on trying to persuade him otherwise. Paimon teases Xiao about Yanfei's comments, which he denies.