Loomian Legacy Petrolith & Underwater Mining Lab

Petrolith fossils are collectible pieces mined at the POLUT Underwater Mining Lab (UMV) — a side-system separate from normal wild catching. Petroliths represent fragments of ancient Loomians preserved in stone. They have no battle use on their own; value comes from combining pieces at the R-SCAB revival station with Soul Crystal energy to resurrect full Loomians, including rare titans and fossil species lines.

This guide explains how UMV mining works, how -A / -B / -C (and sometimes -D) piece sets combine, what pristine one-piece fossils are, and how Secret Ability odds differ from standard wild hunts. Link your fossil grind with Soul Burst if you revive lines that need Burst Crystals, and with How to Catch for baseline encounter skills before diving into lab content.

What is POLUT UMV?

The Underwater Mining Lab sits in the POLUT region’s underwater research chain — unlocked through story progression tied to Lost City Walkthrough and related side routes. Inside UMV, players extract Petrolith items from mining nodes rather than battling wild Loomians in grass.

UMV sessions reward fossil shards, crafting materials, and occasionally complete fossil specimens. Unlike raid or route farming, UMV is inventory-heavy: you stockpile labeled pieces (-A, -B, -C, sometimes -D) until a set is ready for R-SCAB.

Petrolith piece sets and R-SCAB revival

Most fossil Loomians require multiple Petrolith parts named with suffix letters:

• -A, -B, and -C pieces form the standard three-part revival recipe.
• Some species add a -D fragment for four-part sets — check R-SCAB UI before spending Soul Crystal energy so you do not combine the wrong stack.

At R-SCAB, insert a complete set plus the required Soul Crystal energy cost. The machine outputs a living Loomian at a fixed level with normal ability rolls unless Secret Ability procs. Partial sets cannot be revived; store duplicates in labeled PC boxes so -B pieces do not mix across species lines.

Pristine one-piece fossils

A subset of fossils drop as pristine one-piece Petroliths — single items that skip multi-part assembly. These are prized for convenience and trade value because they cut grind time dramatically. Pristine drops are rarer than individual -A/-B/-C shards; community trackers often note them separately on trading boards.

Pristine fossils still roll abilities and personalities on revival like assembled sets. Do not assume pristine means guaranteed Secret Ability — always verify the sigma marker after R-SCAB finishes.

Secret Ability odds on Petrolith revival

Petrolith revival uses its own Secret Ability table, distinct from standard wild grass:

• Without Ability Charm: roughly 1 in 256 per revival for Secret Ability.
• With Ability Charm equipped: roughly 1 in 64 per revival.

These rates mirror special encounter boosts documented in the Secret Ability guide. If you are mass-reviving titans for competitive teams, equip Ability Charm before every R-SCAB session — the fourfold improvement over unboosted revivals adds up quickly across dozens of fossils.

Secret Ability on revived Loomians displays the same purple sigma (Σ) marker as wild or Rally-born specimens. Pair SA hunting with LoomiBoosts planning if you also stack personality or UP tools on the same project.

Titans and fossil species

Titans are oversized or legendary-tier fossil revivals tied to specific Petrolith lines. They often anchor PvE teams, collection goals, and high-value trades. Fossil species generally cannot be found in the wild until revived — UMV is the primary pipeline.

When building a titan project:

1. Map which -A/-B/-C (or -D) pieces your target needs.
2. Mine UMV until the set is complete or trade for missing letters on community hubs.
3. Save Soul Crystal energy for batch revivals during charm-boosted sessions.
4. Audit every revival for SA before investing Training Points or burst crystals from Raid Battles.

Titans revived without SA can still serve story mode; competitive players usually reset grind until sigma appears or trade for an SA parent to feed Rally later.

UMV mining workflow

Efficient UMV farming looks like resource management more than battle skill:

• Clear inventory space before long dives — fossil pieces stack quickly.
• Label boxes by species shorthand (for example, “Titan-X -B pending”).
• Track Soul Crystal energy income from story, dailies, and raids so R-SCAB never stalls mid-set.
• Sync with events that boost mining nodes or drop pristine fossils; check Guides Hub and update posts when POLUT patches land.

Petrolith pieces cannot be equipped or used in battle — they are crafting/revival items only. Scammers occasionally mislabel ordinary items in trades; confirm piece suffix letters on the trade screen.

Connecting to Soul Burst and raids

Revived fossil lines sometimes become Burst Crystal carriers in endgame content. If your titan doubles as a burst ace, read Soul Burst for one-per-battle rules and crystal equip requirements. Crystal income usually flows from Raid Battles rather than UMV directly, so alternate raid days with mining days to avoid burnout.

Trading and collection tips

Duplicate -A pieces for a species you are not targeting still hold trade value — collectors finishing four-part sets pay for single letters. Document pristine fossils with screenshots showing the one-piece icon before listing.

When buying revivals, ask sellers to confirm Ability Charm was active during R-SCAB if they advertise “charm odds.” Charm status is honor-system in peer trades; prefer reviving yourself when SA matters.

Common mistakes

• Combining mismatched letter pieces and wasting Soul Crystal energy.
• Reviving without Ability Charm when hunting Secret Ability at 1/256 instead of 1/64.
• Investing burst crystals on a titan before checking SA or personality spreads.
• Assuming Petrolith items can be held in battle like Burst Crystals.

Related guides

• Secret Ability — sigma odds across hunt types
• Soul Burst — burst crystals after revival
• Lost City Walkthrough — POLUT and UMV unlock path
• How to Catch — baseline catching before lab content
• LoomiBoosts — boost planning for long grinds
• Guides Hub — full tutorial index