Mortal Shell II Achievements — All 53 With Global Unlock Rates

Mortal Shell II has 53 Steam achievements. The list below is complete, read from Valve’s public stats page for App 2584270 on 2026-09-01, with the requirement text Valve publishes and the global unlock rate for every entry. Sixteen are hidden: Valve publishes the name but not the requirement, so the main table says Hidden rather than guessing. A separate table further down gives what the community has decoded for all sixteen, clearly labelled as player-compiled.

Two numbers frame the whole list. This is Not an Achievement — Valve’s requirement text is literally “Complete Mortal Shell II” — sits at 17.3%, so fewer than one in five owners has finished. No Lifer, the full completion achievement, is at 2.9%.

All 53 Mortal Shell II achievements

Sorted by global unlock rate, most common first.

#	Achievement	Requirement	Global unlock
1	You’re More Than a Weapon	Claim your first Shell, Weapon and Sidearm	93.0%
2	Home at Last	Reach Marrowkeep	91.3%
3	Mid Summer?	Enter the Festival	83.7%
4	Forever Alone?	Unlock Tiel	79.7%
5	Arrival	Unlock Proxima	78.0%
6	Haunting Times	Watch your first Shell Memory	70.4%
7	Deep Cuts	Unlock Axe and Dagger	64.7%
8	Old School	Unlock the Forgotten Crossbow	63.9%
9	Wheelie Good Time	Hidden	60.2%
10	Cut You Down to Size	Unlock the Veteran’s Battle Axe	59.3%
11	Vengeance is Mine	Unlock Eredrim	56.7%
12	Big Boi	Unlock Great Martyr’s Blade	55.5%
13	Meat’s Back on the Menu, Boys!	Hidden	51.6%
14	My Brether	Unlock Smert	49.1%
15	Heartless	Unlock Gragu	48.3%
16	Chop Chop	Unlock the Salvaged Trebuchaxe	47.5%
17	Decked Out	Reach the maximum bonding tier for a Shell at the Shellkeeper	46.9%
18	Headcase	Hidden	44.0%
19	Dual Wielding	Unlock the Axatana	43.6%
20	Old Painless	Unlock the Triarch Repeater	39.0%
21	Point Taken	Unlock Black Needle	38.1%
22	Like Clockwork	Unlock the Clockwork Scythe	35.8%
23	Spiked	Unlock the Caged Hystrix	35.7%
24	The Alchemist	Unlock Sariel	35.2%
25	Stop - Hammer Time	Unlock the Obsidian Hammer	33.9%
26	Sester	Hidden	33.9%
27	Over 9000	Max out a Weapon at the Tarforge	33.2%
28	Beautiful Baby	Unlock the Cursed Child	32.4%
29	Speared	Unlock the Ballistazooka	31.9%
30	Something in the deep…	Hidden	31.7%
31	Down with the Thickness	Unlock Lazlo	31.4%
32	It burnssssssssss	Hidden	31.3%
33	Nightmare Fuel	Hidden	28.1%
34	Baghead	Hidden	27.8%
35	Sat Nav	Find all Map Fragments	26.7%
36	Feed Me	Hidden	26.4%
37	Lord of War	Unlock all Weapons	26.1%
38	Shell Seeker	Unlock all Shells	24.3%
39	Heavy Metal	Play all Lute Tracks in the Game	23.9%
40	Guns. Lots of Guns	Unlock all Sidearms	23.8%
41	Ultimate Gainz	Hidden	23.7%
42	Lost Your Head	Hidden	23.7%
43	Bring My Ova Back to Me	Collect all of the Ova	23.1%
44	Praise him!	Hidden	23.1%
45	Ascension	Hidden	21.1%
46	It’s over now?	Hidden	19.8%
47	This is Not an Achievement	Complete Mortal Shell II	17.3%
48	So Fresh, So Clean	Cleanse All Beacons	14.5%
49	No, You Still Can’t Win	Hidden	14.3%
50	Stoned	Find all Tarstones	8.9%
51	Peter’s Perfect Parry	Hidden	5.9%
52	Seeking the Past	Watch all Shell Memories	3.8%
53	No Lifer	Unlock All Achievements for Mortal Shell II	2.9%

What the 16 hidden achievements are

Valve hides the requirement for sixteen entries. A Steam guide, All Achievements in Mortal Shell 2 by аврил лавин (posted 21 August 2026, updated 22 August 2026), decodes all sixteen. Everything in this table is that guide’s claim, not Valve’s text and not a developer statement — it is included because it is specific, checkable, and matches the unlock rates in the official table above.

Achievement	Community-reported requirement	Global unlock
Wheelie Good Time	Defeat Magdalena, the Lady of the Woods	60.2%
Meat’s Back on the Menu, Boys!	Defeat The Lost Child	51.6%
Headcase	Defeat The Nameless Captive	44.0%
Sester	Unlock Sester Genessa (a Shell)	33.9%
Something in the deep…	Defeat Hexapod	31.7%
It burnssssssssss	Defeat Droeg, the Conquerer	31.3%
Nightmare Fuel	Defeat Sir Isaac, the Scholar-Prince	28.1%
Baghead	Complete Baghead’s dialogue sequence and accept his throne	27.8%
Feed Me	Cause Egon to pass away by offering him Gloom	26.4%
Ultimate Gainz	Defeat Malborn Offspring	23.7%
Lost Your Head	Defeat Orrem, the Reclaimed	23.7%
Praise him!	Defeat The Monolith	23.1%
Ascension	”Discover the secret of the Mango” — method not documented	21.1%
It’s over now?	Defeat Zmey, the Unbidden (the final boss)	19.8%
No, You Still Can’t Win	Take the Tar Golem to his minimum health in the prologue	14.3%
Peter’s Perfect Parry	Parry every one of The Nameless Captive’s headspins	5.9%

Eleven of the sixteen are boss kills, which is why this site’s bosses hub was previously so thin: Valve hides every boss name in the achievement list, so the boss roster was invisible until players published it.

Ascension is the one entry nobody has explained. The guide records the requirement — “Discover the secret of the Mango” — and then stops, with no method. At 21.1% it is clearly not obscure in practice, so the knowledge exists somewhere; it just is not written down in the sources checked here.

The 21 unlockables the achievement list names

Twenty-one achievements follow the pattern “Unlock X” — twenty with visible text plus the hidden Sester — and three separate completion achievements confirm the three-category structure: Shell Seeker (all Shells), Lord of War (all Weapons), and Guns. Lots of Guns (all Sidearms).

The split is 8 Shells and 13 Weapons and Sidearms:

Category	Names
Shells (8)	Tiel, Proxima, Eredrim, Smert, Gragu, Sariel, Sester Genessa, Lazlo
Weapons and Sidearms (13)	Axe and Dagger, Forgotten Crossbow, Veteran’s Battle Axe, Great Martyr’s Blade, Salvaged Trebuchaxe, Axatana, Triarch Repeater, Black Needle, Clockwork Scythe, Caged Hystrix, Obsidian Hammer, Cursed Child, Ballistazooka

Where that split comes from. Valve’s own text never says which category a name belongs to, and the obvious shortcut fails: most item rows read “Unlock the Obsidian Hammer” while Shell rows read “Unlock Tiel”, but “Unlock Axe and Dagger” and “Unlock Great Martyr’s Blade” are plainly weapons with no article. The split above comes from аврил лавин’s guide, which groups the names into Shells and Weapons sections, and it is corroborated on the count by a second, independent guide — How to unlock all Shell Memories / get Glimpses by Zyloc (29 August 2026) — which states that the Seeking the Past achievement requires maximum bonding with “all (8) Shells”. Eight also matches the eight playable Shells the Open Beta store page advertised.

Two consequences worth stating plainly, because this site previously had them wrong. Black Needle is a weapon, not a Shell — the missing article made it look like one. And the eighth Shell is Sester Genessa, whose unlock achievement Valve hides, which is why no amount of reading the official list would have produced her. The Shells hub and Weapons hub now follow this split, with the Community label on the rows that depend on it.

The six collectible sets

Six achievements ask for a complete set, which is the clearest official statement of what Mortal Shell II asks you to hunt:

Set	Achievement	Global unlock
Map Fragments	Sat Nav	26.7%
Lute Tracks	Heavy Metal	23.9%
Ova	Bring My Ova Back to Me	23.1%
Beacons (cleanse all)	So Fresh, So Clean	14.5%
Tarstones	Stoned	8.9%
Shell Memories (watch all)	Seeking the Past	3.8%

Valve publishes the category names, not the counts or the locations, so no totals are claimed here. The rates rank the difficulty for you: Map Fragments, Lute Tracks and Ova are cleared by roughly a quarter of players, while Tarstones at 8.9% and Shell Memories at 3.8% are the two that break completion runs. Shell Memories being rarer than the platinum-adjacent achievements above it suggests they are easy to walk past — Haunting Times, for watching your first one, is at 70.4%, so the drop from one to all is severe.

So Fresh, So Clean (Cleanse All Beacons, 14.5%) also confirms that beacons are cleansed rather than merely lit — see the beacons guide.

Systems and places the list confirms

Small facts, but each one is Valve’s own wording:

• Marrowkeep is a place you reach, and reaching it is achievement #2 at 91.3% — an early hub, not a late-game location.
• The Festival is a place you enter (Mid Summer?, 83.7%). Note the exact spelling: launch-day community guides wrote this as “Midsommar?”, but Valve’s text is Mid Summer?.
• The Shellkeeper hosts Shell bonding, and bonding has a maximum tier (Decked Out, 46.9%).
• The Tarforge is where weapons are upgraded, and weapons can be maxed out (Over 9000, 33.2%).
• Shell Memories are watchable cutscene-style content tied to Shells, not a combat system.

Community guides fill in the numbers Valve leaves out, and these are the ones worth knowing before a completion run:

• The Shellkeeper is named Zhirelle, and the bonding cap is Tier IV, at roughly 27 Glimpses per Shell — about 216 for all eight, which is what Seeking the Past requires. Breaking a Glimpse Stone after twenty enemy kills reportedly gives three Glimpses, and up to thirteen Glimpse Stones can be bought from the hub merchant.
• The Tarforge cap is +16.
• There are 49 beacons, but So Fresh, So Clean only needs 46 of them.
• Weapon location maps are sold by a merchant named Merrick in Marrow Keep.
• Map Fragments are marked on the map by raven icons, and the map starts covered by fog of war on a first playthrough.
• Ova come from cleansing beacons and clearing Corrupted Gates, so that set fills in as a by-product of normal progress.

All six of those are player-compiled, from the two guides credited in the sources below. None of them is a developer statement.

The three known missable achievements

A launch-day Steam guide by MaU flagged three achievements as missable, and all three names check out against Valve’s list: Mid Summer? (83.7%), No, You Still Can’t Win (14.3%), and Peter’s Perfect Parry (5.9%). That is a community report, not an official statement of missability — the missable achievements guide records it with its source and date.

Peter’s Perfect Parry at 5.9% is the rarest non-completion achievement in the game apart from Seeking the Past, and it is hidden, so its requirement is unpublished.

Reading the percentages

These are Steam’s global figures across every account that owns the game, read once on 2026-09-01, twelve days after the 20 August 2026 release. They move. Story achievements are always understated this early because a large share of owners have not finished — expect This is Not an Achievement to climb well above 17.3%.

The figures are also PC-only. PlayStation and Xbox trophy rates are tracked separately by those platforms and are not reflected here.

The short version

Fifty-three achievements. Completion sits at 17.3%, full completion at 2.9%. Twenty-one “Unlock X” achievements name every Shell, Weapon and Sidearm in the game — 8 Shells (Tiel, Proxima, Eredrim, Smert, Gragu, Sariel, Sester Genessa, Lazlo) and 13 Weapons and Sidearms — though the split between the two categories comes from player-compiled guides rather than from Valve. Six collectible sets: Map Fragments, Lute Tracks, Ova, Beacons, Tarstones and Shell Memories, with Shell Memories the rarest at 3.8%. Sixteen entries are hidden by Valve; all sixteen have been decoded by the community, and eleven of them are boss kills — Magdalena, The Lost Child, The Nameless Captive, Hexapod, Droeg, Sir Isaac, Orrem, The Monolith, Malborn Offspring, Zmey and the prologue’s Tar Golem.