Here is the full list of all 28 EMPTY SHELL: DEMO achievements.
Leaving Building C
Find 5 documents
Rounds fired: 200
Kills count: 50
Rounds fired: 100
Kills count: 15
Death count: 1
Death count: 10
As big as an elephant
Complete the Demo
Deploy a Gadget
Upgrades Cost: >1000
Use a Device
Complete the Demo on Nightmare difficulty
Complete the Demo on Hard difficulty or higher
Complete the Demo on Medium difficulty or higher
Complete the Demo on Easy difficulty or higher
Kill the Hand in less than 20 seconds on NIGHTMARE difficulty
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
Find 5 secret rooms
Kill her with her own weapon