Here is the full list of all 28 Mirror Forge achievements.
Find the developer.
Find Cageface in the Subway.
Poke the Eye
Find the changing painting in the Facility area.
Complete the game.
Enter the Prison Dimension.
Find Jill.
Reveal the forgotten truth.
Find the book about the Anunnaki in the Mirror Forge Facility.
Read the two papers in the Homeless Shelter.
Find the first Enlil's Tablet.
Uncover what happened to Jane.
Get to the countryside of Goreburg.
Find the 14 Frozen Moments.
Find out who the dark entity is.
Escape the Woman Monster
Inspect the Paper in the drawer in the Long Staircase area.
Escape the Ashes Dimension.
Listen to the audio log in the Maintenance Room.
Find the Silent Hill Easter Egg
Escape the Invisible Monster in the hangar without taking a hit.
Experience the scare in the Hangar facility.
Show Mercy and fry the suffering Depression Monster.
Read the old tome in the Industrial Zone.
See the massive beast in the Industrial Zone.
Make the acid in the Industrial Zone.
Use a Mirror to travel.
Get the Seal of Nur.