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