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