On 21 August 2015 the developer broke the achievements when updated the game. Thankfully you can still earn them by playing an earlier version where they were working properly.

1. Open the Steam console using the following link: steam://nav/console

2. Type: download_depot 369060 369061 86536916247507392 and when the download finished the following message will be displayed on the console: Depot download complete : "C:\Program Files (x86)\Steam\steamapps\content\app_369060\depot_369061" (1 files, manifest 86536916247507392).

3. Go to the folder where the depot is downloaded: C:\Program Files (x86)\Steam\steamapps\content\app_369060\depot_369061, copy the file amygdala.exe and then paste it and replace it on the game's installation folder C:\Program Files (x86)\Steam\steamapps\common\Amygdala.

You can now earn the achievements.

Note 1: If you can't unlock the achievements "Pacifist", "Wickerman" & "What a Waste" then you should type on the Steam console this command: download_depot 369060 369061 2517202891366224660 and try with that version.

Note 2: The Eternal Vengeance achievement requires 20 wizard kills since you are playing an older version. The developer updated the achievement to 15 wizard kills when the achievements were broken.

You should also know that you might experience stuttering on later levels. I managed to earn the Eternal Vengeance achievement and when I reached the 21 level I got the one with the lava which causes stuttering and at some point I was "playing" with 1 fps and then obviously died.