Location: Varies
Prerequisite: Complete Precipice Scenery and Siege of Mount Windless, have 80 Affinity with Bai Jin
Petitioner: None
Reward: Varies; see below

In order to trigger this quest you'll need to complete two prerequisites, in no particular order. First, you need to complete Bai Jin's side quest, Precipice Scenery. Second, you'll need to complete the main story quest Siege of Mount Windless. If you complete Siege of Mount Windless second this side quest will pop up as you're leaving Wudang Sect; otherwise, it will come up once you complete Precipice Scenery, and boost Bai Jin's Affinity to 80.

Learning that Yi has visited the Outer Lands in the north, Bai Jin wants to pay them a visit and drink in the scenery himself. Odd, since he probably came with Yi on that trip, but... whatever. Jin will propose a trip to Xungi Pass, northwest of Wudang Sect.

The group will be stopped briefly by the guards out front of Xungu Pass, and you'll be instructed to check in with General Huang, whom you saved earlier in the game. Head north through the pass and a cut scene will inform you that Huang has a recurring illness, and the Yuan army is likely to take advantage of the situation. Yi offers to help fetch some plans...

... but Jin isn't interested. He decides to leave the party, warning Yi to avoid the more dangerous option of traveling to Linchang City. At this point you appear to only have one option for completing the quest, but in truth there are two ways to handle it - and you'll probably want to go with the unspoken route.

Option 1 - Travel to Valley of Dragons' Slumber

The 'proper' way to do this quest is to travel to Valley of Dragons' Slumber, a short walk northeast of Xungu Pass. Travel east through the entrance until you're in the larger, enemy-filled second half of the pass, then climb up into the hills. Make your way to the east, until you find a large clearing. There are several Yuan Soldiers here, like the other parts of the pass - but there's also a Yuan Runner wandering around. You can tell him apart from the others by the flag on his back.

Take out the Yuan Runner (he's no stronger than any of the other Yuan Soldiers) and he'll drop a Yuan Military Document. Take it back towards Xungu Pass and, along the way, a soldier will tell Yi that Jin found the real document on his own... and was badly injured in the process. 

Return to Xungu Pass and check to the north to watch a cut scene. Jin doesn't survive, and you'll receive Bai Jin's Testament. After the next, sad cut scene you'll receive the Thunderclap Flameball manual, and the quest will end.

Unless you are not using Bai Jin in your party, this is a far from ideal outcome to Outer Lands Scenery. Fortunately, you can avoid Jin's death by taking another route.

Option 2 - Travel to Linchang City

Head to Valley of Dragons' Slumber, as in the previous scenario, but avoid the soldiers completely and run straight east through the pass. Once you return to the world map, travel north to Linchang. Check the south end of the city and you'll find Bai Jin, surrounded by Yuan Soldiers. 

This fight isn't too bad, even if Yi and Jin are fighting on their own. You'll be surrounded by five soldiers, and included is one more powerful Yuan Army Leader. Go after the Leader first with both characters, sticking to the west side of the battlefield. If you're quick you can wipe him out before he can use his Thunderclap Slash. After that you just need to use AOE attacks to pick off the rest of the enemies.

After the cut scene that follows the quest will end, and Bai Jin will survive. You'll receive the Ensnaring Nails manual for winning the day.