Moonscars

Doing this achievement will lock you out of the Cruel Queen achievement. The Cruel Queen takes you to end game to complete, while this achievement can be done at about 75% complete. So if you do not want to play through a second time entirely, do Cruel Queen first. If you have planned ahead (and not run into any bugs), this is the only achievement that requires a second playthrough.

In the Earth Bowels, between Lajos' Rest and Abyssal Warmth mirrors, you can find Horpyna (the old had missing her eyes). If you have found both eyes, you can give them to her upon first meeting her (THIS IS REQUIRED). Afterwards, further on in the Earth Bowels, you will come upon the Holy Silence mirror. On the same floor, all the way to the west of the mirror, is a key item "Incomplete Mould". If you have already talked to the Gargoyles at the Kiln, you will need to return to them. If you haven't, start exploring downward until you find them (you will fight Lajos a second time just before reaching the Kiln). Exhaust their dialogue to reach a point where you bribe them with 10,000 bone dust to use the kiln for you. This gives you the "fired baby clayborn" in the achievement description. Return to Horpyna and exhaust her dialogue to give her the baby clayborn and unlock the achievement.

If you need her eye locations, you can find the right eye just east of the locked gate you need Wanda's key for in the Depths. The left eye is west of The Nursery mirror, past the elevator, in the tiny room on the west side of the pit.

It is required to give Horpyna her eyes back to complete this achievement. Tested on second playthrough, only one NPC can receive the eyes. So again, Cruel Queen is best done before this to save time.