Here is the full list of all 26 EMPTY SHELL: PROLOGUE achievements.
Death count: 1
Kills count: 15
Rounds fired: 100
Death count: 10
Leaving Building C
As big as an elephant
Kills count: 50
Rounds fired: 200
Complete the Prologue
Deploy a Gadget
Upgrades Cost: >1000
Use a Device
Find 5 documents
Complete the Prologue at Nightmare difficulty
Complete the Prologue at Hard difficulty or higher
Complete the Prologue at Medium difficulty or higher
Complete the Prologue at Easy difficulty or higher
Kill 400 Walking Soulless
Kill 10 Spitting Spiders
Kill 350 Small Spiders
Collect all the documents in the Prologue
Finish a level without taking any damaged on NIGHTMARE difficulty
Kill 350 enemies with the Old Axe
Finish a level with only melee weapons
Survive the whole Prologue on NIGHTMARE difficulty with the same volunteer