Diablo 4 Season 15 has adjusted Mythic Upgrade mechanic. Players can now directly upgrade an existing Unique item into a Mythic version while retaining its original stats, Tempering, and Masterworking, all while boosting its Unique Power.
However, Mythic items created via this recipe bear a special Crafting Mark, and you can only equip one such item at a time.
Therefore, the key consideration during the early-to-mid stages of Season 15 is: which Unique item should receive Mythic upgrade to yield the greatest boost in combat power? Usually, the answer is the core piece of gear that offers the most significant benefit to your current build.

What has Changed with Mythic Upgrades?
While Mythic Upgrades in Season 14 involved a high degree of randomness, D4 Season 15 allows players to directly upgrade an existing Unique item into a Mythic one.
Upon upgrading, the original item's Affixes, Tempering, and Masterworking are preserved, and Unique Power is increased by approximately 30%.
Consequently, it is better to farm a target Unique with strong stats first before performing Mythic Upgrade. Note, however, that you can only equip one Mythic item created via this recipe at a time; D4 Mythic items obtained through standard drops or other methods are not subject to this restriction.
How should You Choose Your First Mythic?
Since the supply of Sparks is limited during the early-to-mid stages of Season 15, your first Mythic upgrade should prioritize the core Unique item that provides the greatest benefit to your build.
When selecting a target, consider Unique Power's multiplier. A 20% effect might only rise to around 26% after upgrading - a relatively minor actual gain - whereas upgrading an effect with a high base multiplier yields a much more significant benefit.
Beyond the multiplier, consider whether Diablo 4 items directly contributes to your core damage output, how reliably its effect triggers, and whether the item's Affixes, Tempering, and Masterworking are of high quality. If these conditions aren't ideal, there is no need to rush into spending a Spark, even if the multiplier is high.
Upgrade Order
For the vast majority of builds, start by identifying the most important Diablo 4 Unique items in your current setup and comparing their Unique Powers, trigger frequencies, and impact on core damage output. Once you have identified your highest-priority target, farm a version with better stats, complete Tempering and Masterworking, and finally perform Mythic Upgrade.
After completing the first item, you can leverage this power spike to tackle higher-difficulty content. Faster mob clearing and progression speeds will improve the efficiency of acquiring subsequent gear and resources.
If you later obtain a stronger Mythic for the same slot, you no longer need to reserve your upgrade opportunity for that item; instead, you can shift your focus to the next high-value Unique in your build.
In this way, the priority for Mythic Upgrades shifts dynamically alongside your gear. Prioritize upgrading the item that offers the greatest benefit at your current stage, and only consider the next item once the current one has been replaced by a superior option.

Don't Rush to Use Your First Batch of Sparks
Although it is possible to acquire Sparks early in D4 S15, there is no need to perform a Mythic Upgrade immediately upon obtaining the resource.
If you haven't yet farmed your core Unique, or if the current version's key affixes and enhancement results are mediocre, it is better to continue progressing and farming gear. Since the upgrade preserves the item's current state, investing Sparks too early into a Unique that will soon be replaced yields little return.
The ideal time to upgrade is after you have locked in your build's core gear and possess a version of high enough quality to use reliably for an extended period. This ensures that your first Mythic Upgrade translates effectively into actual combat power.
How Should You Adjust if You Find Another Mythic Later?
The first Mythic you upgrade in D4 S15, doesn't have to occupy that slot forever.
If you subsequently find or craft a stronger Mythic that can replace your current piece, you can re-evaluate the remaining Uniques in your build and shift your upgrade target to the next most beneficial slot.
For example, you might initially prioritize upgrading Unique with the highest damage multiplier; once that slot is replaced by a stronger Mythic obtained through drops or crafting, you can then look at the item with the second-highest multiplier or the one that most significantly affects your build's rotation.
Therefore, the priority list for Mythic Upgrades is not static; it develops as your gear improves. Upgrade the item offering the highest current benefit first, and address the next item only after securing a replacement.
Why does This Change Mid-Game Progression?
In the past, Mythics were rarely included in mid-game builds because consistently obtaining specific items was difficult during that phase.
With the introduction of targeted Mythic Upgrades in Diablo 4 S15, players can upgrade core Unique items into Mythics much earlier. This facilitates an earlier transition into a mid-game setup, providing a reliable boost to combat effectiveness during that phase.
For your first Mythic upgrade in D4 Season 15, prioritize a Unique item that offers a Unique with a high-value Unique Power multiplier, contributes consistently to core damage output, and has a solid base. Choosing the right target ensures a significant power spike in the early-to-mid game, thereby accelerating your subsequent progression.











