Fossil Crafting Explained: Targeted Rolling with Resonators

Goal

Energy Shield prefixes with Dense Fossils: a worked method example

Base

Twilight Regalia for pure ES or Necrotic Armour for evasion/ES, ilvl 86

Method

Prepare base → Dense resonators → separate Eldritch suffix work

In the app

Resonator loading, socketing, applying and target checks on Fossils

Checkpoint

Select defence tiers and matching; stop before changing the finishing side

Guide coverage

Fossil mechanics and ES preparation, not a guaranteed finished ES value

Fossils are one of the most controllable ways to reroll a rare, because they bias the mod pool. Instead of rerolling blind like a Chaos Orb, you socket fossils into a resonator and apply it. The item rerolls with certain kinds of mods made more common, and often others removed entirely.

A practical ES example: base before fossils

For a pure-ES body armour you intend to keep, consider ilvl 86 Twilight Regalia rather than a low-level base that merely rolls an ES modifier. For evasion/ES, consider ilvl 86 Necrotic Armour. The top natural body-armour percentage-defence tier needs 86; requirements differ on smaller armour slots. Base selection and modifier data explain the distinction.

This completed Twilight Regalia report starts with base quality and a chosen fracture, rolls ES prefixes with Dense Fossils, then works on suffixes with Eldritch currency. The useful lesson is the order: prepare the base, roll one half, then protect it while finishing the other. Its exceptional result and historical spend are not an expected budget.

Dense biases defence modifiers; it does not unlock an unavailable tier or make suffixes good automatically. Compare targets in a simulator, and stop the fossil stage before the separate Eldritch finishing.

Set the ES target before loading resonators

For the pure-ES example, use Body Armour → Twilight Regalia in the Mod DB. Choose the acceptable natural flat ES, increased ES, and hybrid increased ES + stun/block recovery prefix families, then All of them if all three are required. Select each lowest acceptable tier rather than a bare numerical ES total. A hybrid is one affix with multiple lines.

On a fractured-prefix base, that prefix is already fixed. The app excludes fractured mods from rolling targets, so put only the remaining rollable prefixes in the target list; check the fracture yourself. Do not request the fractured line as another rolled hit. Confirm the chosen modifier groups can coexist using body-armour modifier data or Craft of Exile, then calibrate the Dense/resonator recipe on the Fossils page. Stop at the prefix checkpoint and inspect before Eldritch suffix work.

Where fossils come from now

Since 3.28, fossils only drop in Delve. GGG removed every other source, but made them much more common behind fractured walls and off the main paths. If you're planning a fossil craft, either delve for them or buy them. The prices on trade reflect that single source.

Resonators and fossils

A resonator has between one and four sockets: Primitive (1), Potent (2), Powerful (3) and Prime (4). You socket that many fossils, then apply the resonator to an item. It works like a Chaos Orb, but with every socketed fossil's effect applied at once.

Each fossil pushes the pool in one direction. A few common ones:

• Pristine — more life mods.
• Dense — more defence mods.
• Frigid / Scorched / Metallic / Aberrant — more cold / fire / lightning / chaos mods.
• Jagged — more physical mods. Serrated — more attack mods. Aetheric — more caster mods.
• Corroded — more poison and bleeding mods.

Many fossils also block a category completely. That matters as much as what they add: every mod taken out of the pool raises your odds on the ones left. Read each fossil's tooltip before combining them, because two fossils can fight each other (a fossil that blocks life won't help a life craft).

Physical clusters: another pool worth comparing

For a physical cluster jewel, choose the small-passive enchantment, number of passives and required notable combination before buying fossils. A Jagged Fossil increases the weight of Physical-tagged mods and blocks Chaos-tagged mods. A notable that benefits a physical build does not necessarily have the Physical tag: inspect the exact cluster's modifier pool first.

Compare Jagged alone with combinations in Craft of Exile. Include the resonator in each attempt's cost, and check that the target notables can coexist as prefixes/suffixes. More fossils are not automatically cheaper. The large-cluster guide explains base selection and why physical-damage wording alone is not enough to select Jagged.

Fractured Fossil changed in 3.29

Fractured Fossil no longer splits or duplicates a base. It now fractures a modifier as part of its craft, and cannot be used on influenced or already-fractured items. The resonator still reforges the item: do not treat it as a way to keep a chosen existing affix. GGG's 3.29 notes also replace the old Bestiary split recipes with Talisman fracture recipes. Old base-copying workflows need a new plan.

Why it's still a grind

Even with a biased pool you rarely hit the perfect item first time. The required applications depend on the exact base, pool and tiers; estimate that recipe in a simulator. Each one means: pick up the resonator, socket the fossils, apply, copy the item, read it, and decide. That's the part worth automating.

Automating it with Exiled Bench

The app's Fossils page runs the whole loop:

1. Choose the fossils you're using, up to four per resonator, and set Target mods from the Mod DB (pick a mod and the lowest tier you'd keep). Choose how it stops (Any one, All of them, or One of each for a key mod plus one from a second list), and add unwanted mods to reroll away bricks.
2. Pick the Resonator and fossil menus, or use Choose… on the fossil-tab picture. Under Calibration, align the fossil-tab frame and set the item position; the app derives the resonator, fossil stacks and socket positions from that frame. There is no separate calibration for every fossil stack.
3. Set a Safety limit, Arm, and press your start key. It loads the resonator, sockets the fossils, applies it and reads the result, and stops when your target combination appears.

Batch it: run it on your Inventory instead of a single item, and the app rolls each base in turn, skips the ones already done, and keeps going until they're all finished or the Safety limit is reached.

Got fossils you'll never use?

Fossils you don't need can be turned into ones you do. The app's Harvest page has a Currency reforge mode: you tick which fossils you're happy to feed, it reforges the stack through Harvest, and it stops the moment the stack becomes something you didn't tick. Prices come live from poe.ninja, and each run reports what went in and what came out, in chaos. See Harvest crafting explained.

Tips

• Buy in bulk if you're batching, so the run doesn't stop halfway to restock.
• Block, don't just add. Some of the strongest fossil crafts are about the mods a fossil removes.
• Decide your minimum tier first. A target of "life, tier 2 or better" stops on a keepable roll, not the first low one.

For a single hard mod, the simpler Alt + Aug approach is often cheaper. For a chest where a physical mod is the goal, see the explode chest guide.

Sources

• Patch notes 3.28.0 — fossils now Delve-only (official forum)
• Fossil — PoE Wiki
• Craft of Exile — simulate fossil odds before you spend