Jah is one of the most valuable runes in Diablo 4 Season 15, mainly because it changes Evade into Teleport. That small change has a huge effect on movement, positioning, and speed. You can cross gaps, escape crowded rooms, and reach objectives much faster. If you are putting together a late-game build, keeping useful D4 items ready can make the farming process feel less punishing while you work towards this rare rune.

Build Your Rune Supply First

Do not rely on one lucky drop. Jah can appear while you are running the Kurast Undercity, but most players will need several attempts. The Jeweler offers another route. Three Legendary runes with the same name and rarity can be exchanged for one new Legendary rune, along with a gold cost. The result is random, so unwanted runes still have value. Keep them instead of selling everything immediately. A simple routine helps.

Store spare Legendary runes after each run.
Check the Jeweler before spending gold elsewhere.
Keep enough materials for several reforging attempts.
Use lower-value drops to maintain a steady supply.

This approach turns ordinary loot into more chances at Jah, even when the dungeon refuses to give you the exact rune.

Make Every Undercity Run Count

Kurast Undercity remains the main place to target high-tier runes. Use a Greater Tribute of Harmony before entering if you have one available. It shifts the reward focus towards runes, which makes the run more worthwhile. Speed matters, but rushing blindly can cost you attunement. Move through dense groups, collect attunement as you go, and keep an eye on the timer. A full reward meter gives the final chest a much better chance to contain useful loot.

Do Not Ignore the Portal Prankster

The Portal Prankster is easy to miss because it appears during an already busy dungeon run. If you find one, take the time to defeat it. Its reward is tied to the end of the run, adding chests beside the exit portal after the boss is down. That extra loot may contain Jah, but it can also provide the runes needed for later reforging. The decision comes down to timing. If the clock is nearly empty, finish the objective first. Otherwise, the detour is often worth taking.

Use Mercenary Rewards Between Runs

Mercenary rapport gives your farming routine another useful layer. As rapport rises through quests and open-world activity, the vendor in the Mercenary Den offers caches bought with bartering currency. These caches can contain runes and other materials. They will not replace Undercity runs, but they help fill the gaps between them. Keep the caches moving, take spare runes to the Jeweler, and use the combined routine to improve your odds without wasting a play session. With patience and a sensible stock of D4 items buy options, the path to Jah becomes much more manageable.