Sanctuary field notes

Diablo IV Field Guide

Researched, versioned notes on Diablo IV systems and decisions.

Season 15: Splinters, Prime Evils, runewords and Nightmares

Scope: Season of Hell’s Legacy, live 3.2.1 rules
Checked: September 27, 2026
Status: Working guide. The seasonal quest and Splinter systems are documented by Blizzard; hidden runewords and exact in-game menus need further verification.

The season has two different Splinter systems. This distinction makes the rest much easier to follow:

Name What it is How you use it
Splinters of Evil Three Prime Evil choices: Diablo, Baal, Mephisto. Bear one at a time for an Iconic combat power, its reputation track and activity modifiers. Change by acquiring and using another Prime Evil Splinter; the large Waking Nightmares are Blizzard’s documented route to more.
Soul Splinters Eight named, socketable seasonal gems, each with a benefit and drawback. Equip up to three across jewelry sockets. Fuse duplicates of the same name and rarity through Cube Amalgamation.

The source for both systems is Blizzard’s Season 15 overview. Blizzard occasionally calls the Prime Evil choice a “Prime Evil Soul Splinter,” which makes the similar names confusing; here “Soul Splinter” means the jewelry gem unless otherwise specified.

The route through the season

  1. Follow the seasonal questline. Deckard Cain’s story takes you through the large Waking Nightmares to fight echoes of Diablo beneath Tristram Cathedral, Baal at Arreat Summit, and Mephisto in the Durance of Hate. These encounters yield the three Prime Evil Splinters.
  2. Pick the power that suits what you want to run. You bear only one Prime Evil Splinter at once. Its power triggers periodically in combat, while its linked activities earn reputation and unlock modifiers and power upgrades through War Plans.
  3. Run that Prime Evil’s activities and Waking Nightmares. Choose a track that overlaps your normal farming. Use the small world encounters and fixed dungeons when you meet them; replay large Prime Evil dungeons on Torment once unlocked.
  4. Socket useful Soul Splinters and combine matching extras. These are a separate jewelry system. Look at both the benefit and drawback before equipping; save matching lower-rarity copies for Amalgamation.
  5. Advance Season Ranks alongside the track. The account-wide Season Rank objectives, Prime Evil reputation, War Plans allocation, and your character’s level/Paragon are separate progress meters. Check the next rank’s objectives and Capstone requirement instead of assuming that filling one reputation bar advances everything.
  6. Experiment with Cube runewords once you have the ingredients. These hidden recipes are documented mainly by players. Check the Cube preview before transmuting and do not spend a valuable base on an unverified combination.

Blizzard lists nine Season Ranks and 125 objectives, with rewards including skill and Paragon points, Mythic caches and crafting materials. About 15% of objectives require Lord of Hatred, including objectives needed to complete Rank VIII and claim every rank reward. Season Blessings are another reward path within Season Ranks; Smoldering Ashes come from objectives and chapter rewards. Season Ranks and Blessings.

Prime Evil Powers: choosing and switching

Prime Evil Splinter Periodic Iconic damage Activities it modifies Decision
Diablo — Terror Fire Helltide and Infernal Hordes Choose if these are your current farming loop.
Baal — Destruction Cold Kurast Undercity and Lair Bosses Choose if you are spending time on tributes and bosses.
Mephisto — Hatred Physical The Pit and Nightmare Dungeons Choose if you are pushing those activities.

All three also modify Tree of Whispers. If you choose Baal to farm Lair Bosses, Mobalytics’ Season 15 boss loot table helps you choose a boss for a specific Unique. That table covers Lair Boss loot, not the Prime Evil echo encounters inside large Waking Nightmares. Each reputation track has eight activity modifiers and six upgrades to its Iconic Power. Bearing a Splinter makes you more vulnerable to the associated Prime Evil, so the choice has a cost as well as a benefit. Blizzard’s Prime Evil description.

How to switch: Return to a large, multi-level Waking Nightmare associated with the Prime Evil you want and obtain its Splinter. Blizzard confirms that acquiring another changes the path you pursue. Players report that the Splinter is a one-use consumable, activated near Deckard Cain’s table in the Imperial Library; check its tooltip before using it, since switching back can require farming another copy. This is not a jewelry gem swap. Afterward, check the seasonal power and track UI to confirm what is active. Exact drop sources, difficulty requirement and whether earned progress on the old track is retained need in-game verification; player reports on these details conflict. Blizzard’s switch rule.

War Plans provide the modifiers and upgrades. In Season 15, War Plans reputation points are shared across your characters only when realm, Hardcore state and Solo Self Found state all match. Characters allocate their shared points on separate planners, so an alt can choose another setup. War Plans sharing rules.

Soul Splinters: what the 5:1 Cube recipe does

The eight jewelry gems are Anguish, Sin, Lies, Black Soulstone, Pain, Mother, Hellfire and Damnation. They drop at Magic → Rare → Legendary → Unique rarities. Equip at most three across available jewelry slots. Every one has a boon and a liability; the best mix depends on your build and tolerance for its drawback. Blizzard’s Soul Splinter list.

In the Horadric Cube, choose Amalgamation and use five copies of the same Soul Splinter name and the same rarity to produce one of the next rarity. The 5:1 count comes from an in-game player observation and is also reported by players on Blizzard’s forum; Blizzard’s announcement confirms the matching type/rarity and one-step upgrade but does not state the count. This is not how you change Prime Evil Powers.

For example, five Magic Splinters of Lies should yield one Rare Splinter of Lies; five different Magic splinters are not a targeted recipe. Check the output preview and whether it retains the item properties you care about before committing expensive copies.

Farming Soul Splinters for Amalgamation

If you are happy with any Soul Splinter, keep playing your usual activities and save matching duplicates. If you want a particular one, start with Nightmare Dungeons that have its matching Gem Reserve affix. Open the Horadric chests in those dungeons and collect every copy of the same name; lower-rarity copies are inputs for the Cube’s 5:1 Amalgamation. Players report that Escalation Nightmare Dungeons are especially useful when the Branching Pathways War Plan node lets you choose a matching Reserve between floors. This is a targeted farming route reported by Helltides and DiabloFilter, not a Blizzard-published drop rate or a measured best-per-hour result.

Soul Splinter you want Matching Nightmare Dungeon Reserve
Anguish (Fire Resistance) Ruby
Sin (Lightning Resistance) Topaz
Lies (Cold Resistance) Sapphire
Pain (Poison Resistance) Emerald
Damnation (Shadow Resistance) Amethyst
Hellfire (All Elemental Resistance) Diamond
Mother (Physical Resistance) Skull

Black Soulstone gives All Stats and has no corresponding resistance gem, so this Reserve matching method cannot target it. For an ordinary Nightmare Dungeon, inspect the sigil’s Reserve affix before using it. In an Escalation, select the desired Reserve when Branching Pathways offers it; open the Horadric chests rather than rushing only to the boss. Other activities can award random Soul Splinters, including the Infernal Hordes gem chest, but the Reserve route is the useful choice when you need one named type. Blizzard does not specify a guaranteed jewelry Soul Splinter from each seasonal Waking Nightmare, or publish evidence that those dungeons have a higher jewelry Splinter rate. The seasonal quest’s three Splinters of Evil are different rewards. The mapping and chest behavior above are community findings; the exact chest and boss odds, and how difficulty changes rarity, still need controlled in-game checks.

The 5:1 recipe compounds quickly: 5 Magic → 1 Rare, 25 Magic → 1 Legendary, 125 Magic → 1 Unique if none drops at a higher rarity. Keep matching Rare or Legendary drops too; each skips much of that chain. Blizzard confirms that Amalgamation combines Soul Splinters of the same type and rarity. Check the Cube’s output preview before consuming five copies.

Jeweler warning: “Salvage All Gems” includes Soul Splinters. Players have confirmed that the bulk command consumes their unsocketed Soul Splinters and returns ordinary gem fragments. It does not preserve them for later Amalgamation, and those fragments cannot be turned back into Soul Splinters. Player report and confirmation. Move the Soul Splinters you intend to keep into your stash before using the bulk gem salvage command, or salvage ordinary gems individually. Blizzard describes Soul Splinters as special gems; the precise fragment yield from salvaging one has not been verified here.

What are Waking Nightmares?

Size What you encounter Role in progression
Large Prime Evil Nightmare Multi-level, fixed-difficulty Capstone-style dungeon ending in a Prime Evil echo. First visited in the seasonal story; later replayed for rewards on Torment. Use these to obtain a different Prime Evil Splinter. Versions at Torment 10+ provide a pinnacle challenge.
Standard-length Nightmare A fixed dungeon location revisiting older Diablo scenes, such as the Den of Evil. An additional seasonal dungeon to discover and clear.
Small open-world Nightmare A sudden one-room encounter with a past boss or monster waves. A short, opportunistic event while roaming.

These are Waking Nightmares, a seasonal family of encounters. The smaller and standard versions are not the large Prime Evil encounter used for switching your power. Do not confuse them with ordinary Nightmare Dungeons, which are also one of Mephisto’s modified activities. Blizzard’s three Nightmare types.

Optional Old Tristram secrets (spoilers)

Shared entrance: Community guides report that reading ten Deckard Cain journals unlocks a return to Cain at the Imperial Library and his Deckard’s Memory portal to Old Tristram. Mobalytics’ Harlequin Crest route has a journal location map. Blizzard’s season announcement alludes to hidden discoveries but does not spell out these secret quests; the steps below come from community documentation.

Goal Once inside Old Tristram Cost and result
Harlequin Crest (Shako) Talk to Ogden for the tavern-sign quest. Return to Diablo’s Labyrinth, speak to Snotspill for the key, find the sign chest on that floor, then bring the sign to Ogden. Mobalytics reports a Mythic Harlequin Crest reward. This route uses the journal entrance; it does not require Cubing the three Prime Evil Splinters into Wirt’s coins. Ogden’s Sign walkthrough.
Hellfire Torch Collect one each Terror, Destruction and Hatred consumable, Cube them into Wirt’s Lucky Coins, and use the coins at Tristram’s fountain to open the Uber Tristram encounter with three Prime Evil echoes. Mobalytics reports a Mythic Charm reward. These three Splinters are consumed for the coin and cannot then be used to switch your active Prime Evil. Hellfire Torch walkthrough.

Before spending rare Splinters: Mobalytics says replacement Splinters begin dropping at Torment 10, but players report some drops below that tier; check your own difficulty and source. Multiple player bug reports describe the fountain consuming the coin without opening the portal. Whether the bug has been fixed on the live build is unconfirmed; check before committing a hard-won coin. Both secret rewards and exact quest requirements need in-game confirmation.

Seasonal runewords: the hidden Cube route

Players have found Diablo II-inspired Cube recipes that turn a Common (white) base item plus a particular set of runes into a named item. This was not laid out in Blizzard’s Season 15 overview. Mobalytics’ Season 15 runeword guide provides a convenient recipe catalogue, eligible bases and rune upgrade recipes; the practical steps are also described by players on Blizzard’s forum. Treat the catalogue and resulting powers as community findings until checked in game.

First example: Stealth. Obtain Tal + Eth and a white chest armor, put all three into the Horadric Cube, and inspect the resulting recipe/output before transmuting. A Rare (yellow) chest with sockets is not the white base this recipe calls for. Community reports say the seasonal quest supplies an early base and runes, but check your quest rewards rather than assuming the exact timing. If crafting a later version, the base item’s quality and level matter; read the preview first.

This differs from the ordinary Diablo IV socket runeword: a Rune of Ritual and Rune of Invocation placed into a two-socket item trigger an effect. The seasonal Cube item recipe consumes a white item and the specified runes to create a named piece of gear. Do not put Tal and Eth into armor sockets expecting to craft Stealth. Blizzard’s original socket runeword explanation; current player Cube instructions.

Caution: early community posts described a three-Stealth transmutation that granted Teleport; later player reports say this behavior was removed. Do not plan a build around an old exploit or assume a runeword will inherit a power from a different named item. Player reports after the change. Rune return on salvage, eligible bases and item-specific results still need live confirmation; cross-check any recipe from the community catalogue against your current Cube preview.

In-game checks for the next revision

  • Capture the seasonal UI after switching from one Prime Evil to another: consumable action near Cain’s table, active power, old/new reputation, upgrade points, and exact entrance/difficulty.
  • Check one Amalgamation preview for five matching Soul Splinters, including the new rarity and whether any roll changes.
  • Compare matching Gem Reserve runs in normal and Escalation Nightmare Dungeons: record chest and boss Splinter names, rarities and drops per run. Separately test the Jeweler’s individual Soul Splinter salvage preview and resulting fragment type and quantity with a disposable copy; never use bulk salvage for the test.
  • Record one Cube runeword result from a disposable white base: inputs, displayed recipe (“???” if hidden), output, and whether the base/runes are consumed.
  • Check which Waking Nightmare icons correspond to large, fixed-dungeon and world-portal encounters, and what each actually awards at your difficulty.
  • Record which Season Rank requires which Capstone and which objectives require the expansion. Keep the season rank, Prime Evil reputation, and War Plans point allocation distinct.
  • Before consuming Wirt’s Lucky Coins, check current patch/bug status and record the portal behavior; verify the coin and Torch outputs independently of the community walkthrough.

These sources and tools document the season’s less obvious routes. Thanks to the creators whose work made those routes easier to investigate. Links beside consequential claims point to the relevant evidence.