Full list of all 25 Mortal Shell achievements worth 1,000 gamerscore. It takes around 15-20 hours to unlock all of the achievements on Xbox One.
Beat the game without ever bonding with a shell.
Defeat Hadern in the tutorial
Unlock all secret lore
Pick 50 mushrooms
Kill an enemy with a bear trap.
Beat the game in obsidian dark form.
Waste your life away with Baghead.
Become familiar with all items.
Find your first Shell.
Kill an enemy by kicking them off a platform.
Bring a gland to Dark Father.
Jam with a brigand.
Spend over 50,000 Tar in the Vlas's Shop
Parry over 100 attacks.
Unlock all of the Shells in the game.
Defeat all the different versions of Grisha.
Complete Mortal Shell.
Defeat Imrod, the Unrepentant.
Defeat Tarsus, the First Martyr.
Defeat Crucix, the Twiceborn.
Defeat The Unchained.
Kill two or more enemies with one shot from the balistazooka.
Kill an enemy with a hardened plunge.
Renounce humankind.
Pet Vlas's cat.