Mortal Shell II Achievements Guide: All 53 Confirmed

Updated 2026-10-05: Steam's all-language review endpoint now reports Mostly Positive with 17,040 positive and 4,532 negative reviews, 21,572 total.

TL;DR: Mortal Shell II has 53 total achievements, confirmed via Steam's own stats page. All 8 Shells are named (Tiel, Proxima, Eredrim, Gragu, Smert, Sariel, Lazlo, Cursed Child), matching this site's own review. The rarest achievement, No Lifer, sits at just 4.3% of players. This guide does not attempt a full boss list, since even the community's own boss-guide authors are still disputing the exact order weeks after launch.

How many achievements does Mortal Shell II have? (quick answer)

53. Steam's public Community stats page for Mortal Shell II lists all 53 by name and unlock percentage. Most, roughly two-thirds, include a visible description tied to unlocking a specific Shell, weapon, or Sidearm. The remaining third are hidden until earned, which fits a souls-like's usual mix of story-spoiler and secret-discovery achievements.

Key takeaways

• 53 total achievements, all base game, confirmed directly from Steam's Community stats page.
• All 8 Shells are individually named and achievement-tracked: Tiel, Proxima, Eredrim, Gragu, Smert, Sariel, Lazlo, and the Cursed Child.
• The rarest achievement is No Lifer (4.3%), for unlocking every other achievement in the game.
• This guide does not include a full boss list. A Reddit thread from Mortal Shell II's own community boss-guide creators shows active disagreement over the order of the 10 main bosses, on top of dozens more reused enemy-type "bosses."
• At least 15 weapons are individually confirmed by name through their own unlock achievements.
• Mortal Shell II launched August 20, 2026 at $49.99 and currently has 21,572 all-language Steam reviews, with 17,040 positive and 4,532 negative.
• Still deciding whether to buy? Read the full review first.

Why this guide skips a full boss list

Souls-like achievement guides on this site usually name every boss. This one doesn't, and it's worth explaining why rather than just leaving the gap. Our own Mortal Shell II parry guide, written the same week the game launched, explicitly declined to publish a boss-by-boss breakdown, calling it "guessing ahead of what's actually been mapped out." Weeks later, that caution still checks out: a Reddit thread from a group actively building Mortal Shell II boss guides describes finishing content for "10 main bosses" while noting the game has roughly 45 boss-tagged enemies in total, and a commenter on that same thread directly disputes the order of that 10-boss list. Our own Mortal Shell II review adds a related complication: it flags the campaign's back half for leaning on "recycled regular enemies standing in as bosses," which is exactly the kind of ambiguity that makes an authoritative main-boss count hard to pin down from outside the community's own ongoing debate.

Publishing a confident "all bosses" list against that backdrop would mean picking a side in an unresolved disagreement and presenting it as settled fact. This guide sticks to what Steam's own achievement data actually confirms instead.

All 8 Shells, confirmed

Each Shell has its own dedicated unlock achievement, and together they match this site's review, which counted "eight possessable Shells" giving the game real build variety.

Tiel and Proxima both sit well above 79%, meaning most players encounter them naturally within the opening hours. The remaining six drop off more steeply, in the 36-60% range, suggesting they're tied to further exploration or later-game areas rather than the critical path. Shell Seeker (29.0%), the achievement for unlocking all 8, sits below every individual Shell achievement except the two most common, which tracks: collecting every Shell means finding the least common ones too.

GODEEPER: For how each Shell actually plays once you've got it, this site's parry guide breaks down how Shell choice interacts with block and parry timing. Mortal Shell II Parry Guide →

Weapons and Sidearms, confirmed by name

At least 15 weapons are individually confirmed through their own unlock achievements, sorted here by rarity.

Weapon variety is a core part of Mortal Shell II's build system, and the swamp regions are where several of the rarer, mid-game weapons on this list turn up.

Lord of War (31.3%) tracks unlocking every weapon in the game, and Guns. Lots of Guns (28.6%) does the same for every Sidearm. Both sit noticeably below any single named weapon achievement, which is the expected pattern: a full-collection achievement is always going to be rarer than any one piece of the set it's built from. This site's weapons tier list ranks several of these by combat performance, worth checking before deciding which ones to chase first.

Progression, exploration, and collection achievements

Beyond Shells and weapons, a separate cluster of achievements tracks broader completion goals.

This is Not an Achievement, the achievement for simply completing the campaign, sits at only 22.9%. Compared to a launch-window player base, that's a real signal about how far players actually get, and it's consistent with the review's own finding that the game's difficulty and quality curve isn't even across its full length. Seeking the Past (watch all Shell Memories, 5.6%) and No Lifer (4.3%) are the two genuinely rare completionist achievements on the entire list, both requiring meaningfully more than a single clean playthrough.

Encounters like this one populate the mid-to-late game, part of why the exact boundary between "boss" and "tough regular enemy" is still being debated in the community weeks after launch.

The hidden achievements

18 of the 53 achievements show no description until unlocked: Wheelie Good Time (62.8%), Meat's Back on the Menu, Boys! (55.5%), Headcase (48.9%), Sester (38.6%), Something in the deep... (37.7%), It burnssssssssss (37.5%), Nightmare Fuel (34.4%), Baghead (30.4%), Lost Your Head (30.2%), Ultimate Gainz (30.1%), Feed Me (30.1%), Praise him! (29.6%), It's over now? (25.9%), Ascension (23.9%), No, You Still Can't Win (15.4%), and Peter's Perfect Parry (7.2%). This guide isn't going to guess what any of them require. Several names (Peter's Perfect Parry especially) hint strongly at what they're tied to, but a hint isn't a confirmed source, and this site doesn't publish invented unlock conditions.

Step-by-Step: a sensible completion order

1. Play through normally for your first Shell and weapon: You're More Than a Weapon (93.3%) and the early Shell achievements fire from ordinary progress, so there's no need to plan around them.

2. Prioritize exploration over a straight critical-path run: Tiel and Proxima come easily, but the remaining 6 Shells and most weapons sit in the 30-60% range, meaning they take deliberate detours to find.

3. Watch every Shell Memory as you find them: Haunting Times only needs the first one, but Seeking the Past (5.6%) needs all of them, and this is far easier to track during a first playthrough than to backtrack for later.

4. Max out gear deliberately once your build is settled: Decked Out and Over 9000 both require investing resources at a specific NPC (the Shellkeeper and the Tarforge respectively), so don't spread upgrade materials too thin across builds you're not committing to.

5. Treat full completion as a second-playthrough goal: with This is Not an Achievement itself sitting at 22.9%, No Lifer at 4.3% is realistically not a single-run target for most players.

Frequently Asked Questions

How many achievements does Mortal Shell II have? 53 total, confirmed directly from the game's public Steam Community stats page. Most track weapon and Shell unlocks; roughly a third are hidden and don't show a description until earned.

How many Shells are in Mortal Shell II? 8, each with its own achievement: Tiel, Proxima, Eredrim, Gragu, Smert, Sariel, Lazlo, and the Cursed Child. This matches the 8 possessable Shells confirmed in this site's own Mortal Shell II review.

Does this guide include a full boss list? No, deliberately. A community thread discussing Mortal Shell II's own player-made boss guides shows active disagreement over the exact order and count of the 10 main bosses, on top of dozens more enemy-type bosses the game reuses. Publishing a confident list right now would mean guessing.

What is the rarest achievement in Mortal Shell II? No Lifer, at 4.3% of players, for unlocking every other achievement in the game. Seeking the Past (5.6%, watch all Shell Memories) and Peter's Perfect Parry (7.2%, hidden) are the next rarest.

How many weapons are in Mortal Shell II? At least 15 are confirmed by name through individual unlock achievements, from the Axe and Dagger (66.2% of players) to the Ballistazooka (37.0%). Lord of War (31.3%) tracks unlocking every weapon in the game.

Is Mortal Shell II worth 100 percent completing? That depends on how you feel about the back half of the campaign. This site's review flagged the game's final third as noticeably weaker than its opening hours, and No Lifer sitting at just 4.3% suggests most players who could push for full completion decide not to.

Related Reading

• Mortal Shell II Complete Guide: 8 Shells, Seals, and Gates: the central hub connecting Shells, Seals, weapons, gates, bosses, and patches.
• Mortal Shell II Review: Great Combat, Rough Second Half: this site's full verdict, including the back-half issues referenced throughout this guide.
• Mortal Shell II Parry Guide: block and parry mechanics for all four Seals, plus the original explanation for why a boss list wasn't published at launch.
• Mortal Shell II Weapons Tier List: a ranked breakdown of the weapons named in this guide's achievement list.
• The Mermaid Mask Achievements Guide: another Steam-sourced achievement breakdown that stops short of guessing undocumented triggers.
• Gamble With Your Friends Achievements Guide: a completely different genre, same Steam-first verification method.

References

• Mortal Shell II on Steam: official store page, price, and review data.
• Mortal Shell II Steam Community Achievements: the primary source for every achievement name, description, and unlock rate in this guide.