The Big Guy In Stage 13

 
This dude, vibing behind the spike wall, is the only other “big” secret that I’ve found thus far. 
 
 
Encountering and killing him without anything happening made me think the achievement might be bugged, but I came to realize that its description mentions an imp (remember the tutorial? They are the little winged ones) so I kept looking in other levels. 
 
 

Glitch Imp Location

• Choose your monster. 
• Choose stage 4. 
• Run to the left until you see a portal. 
• Enter the portal. 
• Follow this map.

Map

Other

• Don’t worry about the timer, you won’t actually have to kill the imp/escape the level to obtain the achievement. If you don’t unlock it upon entering his little room: Kill him and finish the level, that should do the trick. 
• Have a nice day 🙂

This is all about From Shadows – “It’s not a glitch – It’s a feature” Achievement; I hope you enjoy reading the Guide! If you feel like we should add more information or we forget/mistake, please let us know via commenting below, and thanks! See you soon!