Main Walkthrough

Location: Skylinemont
Prerequisite: Complete Four Martial Arts Families
Petitioner: Madam Mu
Reward: Pearlflower Spear Martial Art

In order to trigger this quest you need to both complete Four Martial Arts Families, the second quest in Lü Xian'er's storyline, and find Madam Mu, who appeared in Four Martial Arts Families. She disappears at the end of that quest, and the only hint you receive is that she probably lives somewhere 'near' Tianshui City.

If this is your first visit to Tianshui City then you're pursuing the main story at the same time, and you'll need to visit the nearby Skylinemont. Head west of Tianshui to find Skylinemont in the mountains. Proceed through this area, as far as you can go, and you'll wind up on the west side of the Valley area. Look east of the clearing where you find some animal bones and you'll find Madam Mu, standing by herself.

Mu has no interest in taking on a new disciple, though she nevertheless provides Xian'er with a challenge to complete: Travel to Longmen Canyon and defeat ten Longmen Yuan Soldiers. This is quite a trek from Skylinemont, so here are some directions:
  • Travel east to - and through - Fancheng City
  • Travel northeast from Fancheng City to the Xungu Pass
  • Travel northwest of the Xungu Pass, through the desert, until the path curves east
  • Continue following the road to find Longmen Canyon, in the canyon walls
Longmen Canyon is crawling with Yuan Elite Soldiers and Leaders, and they're not much more difficult than the normal variety that you've fought earlier in the game. Defeat ten of them, however, and you'll trigger a cut scene where your party is surrounded by... 

Yuan General

... well... ten soldiers more, to be perfectly honest. And one of them is a general with tons of HP, who knows Thunderclap Slash. Ouch.

This fight is quite a bit more difficult, and you'll want to move your whole party to one side of the battlefield to buy yourself a round before all ten soldiers try to crush your team. Leave the Yuan General for last, as trying to take him out first takes way too long. AOE attacks are a godsend. 

(Note that if you leave Xian'er out of your party formation while fighting soldiers earlier she will be forced into the party for this fight, giving you six party members rather than five.)

You'll receive a bunch of high-power equipment for winning this fight. (I received a Fangtian Huaji and the Tiefutu Armor Advanced Blueprint, though I'm not sure if everyone gets these.) After a few cut scenes you'll be back in Skylinemont, and Xian'er will learn the Pearlflower Spear Unique Move.