Last updated: 5 September 2026
Mortal Shell 2 Tarstones Guide — How Upgrading Actually Works
Tarstones are Mortal Shell 2's main build-crafting layer, but the game doesn't explain the upgrade path clearly: the Tarforge looks like it should let you upgrade a Tarstone the moment you get it, and it won't, until you track down one specific quest item. Here's how the whole system actually fits together.
Tarstones are the passive-effect infusions you slot into Shells, weapons, and abilities — you get 10 slots total (4 shell-compatible, 2 Combat, 2 Infusion, 2 Ability). They only gain XP while equipped and fighting, and the Tarforge in Marrow Keep won't offer upgrades past level 1 until you find the Etching Needle in the Glutted Mire and hand it to Franz. After that, level 2 costs Coins and level 3 costs Tarcores, which you get by leveling other Tarstones to their breakpoints — so don't expect to max every stone you own in one playthrough.
01What Tarstones Are and Where They Slot In
Tarstones are equipment infusions that grant a passive effect or modify an action — anything from a straight damage increase to changing how an attack behaves or boosting crit chance. They come in five types: Support, Combat, Infusion, Ability, and Fragile.
You can have 10 Tarstones equipped at once: 4 shell-compatible slots (tied to whichever Shell you're wearing), 2 Combat slots, 2 Infusion slots, and 2 Ability slots. You'll find new ones through story progression, dungeon chests, boss drops, and purchases from NPCs like Merrick in Marrow Keep.
02How Tarstones Level Up
A Tarstone only gains XP while it's equipped and you're killing enemies with it slotted in — sitting in your inventory does nothing. You don't need to actively use its effect in combat, just have it socketed, so it's worth slotting new Tarstones in early rather than saving them for later.
Tarstones progress through up to 4 levels, and each level requires re-earning XP from scratch with escalating requirements, so higher levels take meaningfully longer than the first.
03Unlocking Tarforge Upgrades: The Etching Needle
Reaching level 1 through XP happens passively, but the Tarforge in Marrow Keep won't let you push a Tarstone past that until you find the Etching Needle, a key item sitting in a chest in the Glutted Mire — the swamp dungeon under one of Fainweald's Corrupted Gates, tucked between a tree and a lit torch, before the Lady of the Woods boss arena.
Bring the Etching Needle back to Franz at the Tarforge in Marrow Keep. Handing it over is what unlocks the actual upgrade option the next time you interact with the Tarforge — until then, the menu exists but does nothing useful.
04What Upgrades Cost
Once the Etching Needle is turned in, a Tarstone that's already hit level 1 through XP can be upgraded to level 2 using Coins at the Tarforge — the Coin cost climbs at each tier, so don't assume level 3 costs the same as level 2.
Getting to level 3 and beyond costs Tarcores instead of Coins. Tarcores come from leveling up your other Tarstones, which means the system is deliberately self-limiting: you can't just grind Coins to max out one Tarstone in isolation, you need a spread of leveled stones feeding into it.
05You Won't Max Every Tarstone — Pick Favorites Early
Because Tarcores are generated by leveling other Tarstones, it's not realistically possible to max out every Tarstone you pick up across a single playthrough. Figure out which 2-3 Tarstones actually matter for your build — see our weapons tier list for which weapons have standout Tarstone synergies — and commit your XP grinding and Tarcores to those instead of spreading effort across everything you find.
A Week 1 Update patch made the early game less punishing here: Tarstones now yield more materials when they break, and some can be bought directly from merchants, so replacing a Tarstone you committed to the wrong slot is less of a setback than it was at launch.
FAQ
How many Tarstones can you equip in Mortal Shell 2?
10 total: 4 shell-compatible slots, plus 2 each for Combat, Infusion, and Ability.
Why won't the Tarforge let me upgrade my Tarstones?
You need the Etching Needle first, a key item found in a chest in the Glutted Mire dungeon in Fainweald. Give it to Franz at the Tarforge in Marrow Keep — that's what unlocks the upgrade option.
How do Tarstones gain XP?
By being equipped while you kill enemies. You don't have to actively trigger their effect, just have them slotted in — Tarstones sitting unequipped in your inventory never level up.
What are Tarcores used for?
Tarcores are needed to push a Tarstone to level 3 and beyond at the Tarforge, once Coins alone stop being enough. You get Tarcores by leveling up your other Tarstones.
Can you max out every Tarstone in one playthrough?
No. Tarcore generation is tied to leveling other Tarstones, so there isn't enough material in a single run to fully max every stone you collect. Pick a handful that matter for your build and focus on those.
Sources
Where the facts on this page were checked. If one of them now says something different, we want to know — tell us and we will fix the guide.
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