Here is the full list of all 38 Styx: Shards of Darkness achievements. It takes around 25-30 hours to unlock all of the achievements on Windows.
Unlock all achievements
Unlock Gold level for all Insignias in all missions
Unlock all skills
Get out alive from 10 red alerts
Kill 5 guards with acid traps
Be saved by a Life-saving Clone
Give of yourself to the worship of Lyssril...
Unlock your first ultimate skill
Remain invisible for a total of one minute
Unlock Gold level for all Insignias in a mission
Finish a mission with the gold Insignia of Swiftness
Finish Mission 9
Finish a mission with the gold Insignia of Mercy
Finish Mission 8
Finish Mission 7
Finish Mission 6
Finish Mission 5
Finish Mission 4
Finish Mission 3
Teleport 20 times into a clone (with the skill)
Kill all the enemies in a zone
Push 10 enemies over the edge
Pickpocket 10 enemies
Kill an enemy in his sleep
Craft 30 items
Collect 50 raw materials
Create 50 clones
Being invisible in a chest and not being caught by an enemy on a search
Drink 25 vials of amber
Dissolve 10 enemies (vial of acid)
Finish a mission with the gold Insignia of the Shadow
Finish Mission 2
Finish Mission 1
Having hidden 50 times in a duct or a hideout
Finish a mission with the gold Insignia of the Thief
Finish the introduction
Finish a level without taking damage
Complete a level without using an amber power