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