IMPORTANT NOTE:

As of the current patch (December 2023), the jade items are no longer guaranteed spawn. However, I will leave this guide on Steam as they are still randomized spot in case you need some additional bei to spend.

The content in the guide below has not been edited, but I've changed the name of the guide to explain the changes.

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The farming location is the first gate (where you get Suwam to dance and open the door for you) in the upper right of the Glacial Area.

The cave's location

Inside this cave-like gate are guaranteed 2 jade plates, 4 jade marbles, and 1 mining spot. They are a guaranteed spawn, so no cheating needed, only your diligence to visit this place twice per day.

4 Jade Marbles = 120 Bei
2 Jade Plates = 120 Bei

= 240 per run

= 480 per day

What I will highlight in this guide is the optimum item collecting route, see the following images for details.

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1. Once you're in, follow the light downward to the first jade marble.
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2. Head right and collect the second jade marble on the stairs.
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3. Keep your eyes on the floor while swimming right. You will see your first jade plate on the floor.
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4. Swim right until you see the wall, mine the mineral if you want, then continue up and pick up the second jade plate from beside the pinball machine.
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5. Head left along the corridor, pick up the remaining two jade marbles along the way. Exit via the left lever.
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You'll notice that your exit triggers the trap like your first visit, but this is nothing since we got all the items. Sell them at Duwa.
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Now that concludes this guide. You may also consider picking up the jade pedestal from the third gate, but the spawn of the pedestal is pretty random, so I didn't include it here.

I hope this helps. :)