Diablo 4 Season 14 Guide: How to Farm Infinite Gems and Runes with the Kurast Undercity Merchant Bug

Summary

Are you struggling to collect enough Gems and Runes for your Season 14 character upgrades? The new Kurast Undercity merchant bug provides a temporary farming method that allows players to repeatedly purchase certain items when the merchant’s inventory appears with duplicated stock. This guide explains the complete process, from setting up War Plans to finding the correct merchant inventory, so you can avoid wasting runs and focus on the items you actually need.

Part 1: Prepare the Correct War Plans Setup

Why This Setup Matters

The first step is preparing the right War Plans nodes in Kurast Undercity. Without the correct setup, the special merchant will not appear consistently.

The required node is Bull Warrior Day. When you defeat a Prankster Goblin during a Kurast Undercity run, this node allows a merchant to appear at the end of the activity. This merchant is the key to the infinite Gem and Rune farming method.

If you have extra War Plans points, also activate the Gutter Filth node. It is not mandatory, but it increases the chance of encountering a Prankster Goblin whenever you activate a beacon inside Kurast Undercity. This makes finding the merchant much faster.

Before starting your runs, check your setup:

Activate Bull Warrior Day.

Add Gutter Filth if available.

Enter Kurast Undercity and prepare for multiple runs if needed.

Part 2: Find the Prankster Goblin and Unlock the Merchant

How to Trigger the Merchant

Once your War Plans are ready, enter Kurast Undercity.

You do not need a special Tribute for this method. During the run, activate all available beacons because they increase your chances of finding a Prankster Goblin.

Follow this sequence:

Enter Kurast Undercity.

Activate every beacon you encounter.

Search for a Prankster Goblin.

Defeat the Prankster Goblin.

Complete the dungeon by defeating the final boss.

Check the merchant that appears at the end.

If you do not find a Prankster Goblin, simply repeat Kurast Undercity runs until one appears. The Gutter Filth node improves your chances, but it does not guarantee a spawn.

Part 3: Identify the Infinite Stock Items

Why Some Items Become Unlimited

Normally, this merchant is not especially valuable because the inventory sells out quickly. However, the current bug affects items that appear with duplicated stock.

When checking the merchant:

If an item appears once, it is normal stock.

If an item appears twice, that item can be purchased infinitely.

Your goal is to find valuable duplicated items, such as:

Legendary Runes.

Royal Gems.

Other high-value upgrade materials.

The important detail is not the item type alone, but whether the merchant shows two copies of that item. Only duplicated stock benefits from the bug.

Part 4: Reset Merchant Inventory Correctly

Incorrect or Correct Methods

A common mistake is spending too many resources trying to force the perfect merchant inventory.

The recommended method is:

Correct method:

Check the merchant’s first inventory.

If you see a duplicated valuable item, buy it repeatedly.

If the inventory is poor, use the free reset once.

Check again.

If the second inventory is still bad, leave and run Kurast Undercity again.

The merchant can be reset once for free. After that, additional resets require a large amount of Forgotten Souls, which is generally not recommended for this farming method.

Avoid repeatedly paying expensive reset costs. It is usually more efficient to complete another Kurast Undercity run and search for a better merchant.

Part 5: Farming Strategy and Resource Management

How to Make the Most of the Bug

Once you find a duplicated valuable item, continue purchasing it as long as you have enough Gold.

The method does not remove the Gold requirement, but Gold is currently much easier to obtain compared with rare upgrade materials.

For players who prefer saving time rather than repeatedly farming materials, some players may consider external trading options such as buy Diablo 4 Items, but the in-game merchant method provides a direct way to obtain Gems and Runes through gameplay while the bug remains available.

A practical farming loop is:

Prepare War Plans.

Run Kurast Undercity.

Kill Prankster Goblin.

Defeat the boss.

Check merchant inventory.

Buy duplicated Gems or Runes.

Repeat until you have enough materials.

Key Takeaways

Activate Bull Warrior Day before attempting this method.

Use Gutter Filth to increase Prankster Goblin encounters.

Always activate beacons inside Kurast Undercity.

The merchant only becomes valuable when an item appears twice.

Prioritize duplicated Legendary Runes and Royal Gems.

Use the free merchant reset first; avoid expensive resets.

Conclusion

The Season 14 Kurast Undercity merchant bug offers a simple farming route for players who need more Gems and Runes without spending countless hours searching for drops. The method depends entirely on finding the correct merchant inventory, so efficient runs and careful resets are more important than rushing through the activity. Until the bug is changed, this strategy provides a practical way to improve your character progression with fewer resource bottlenecks.