Smith Goibhniu

[FieserMoep]

Has someone found the key?

[NasqanSel]

The "key" is the purple miners casque (helmet) you get from clearing the caved mine. You can only do the mine after hearing about the 'buried alive' rumour and going there at night.
Once you have the miners helmet, go back to the smith and he will give you a password to enter Hoenhiem ruins. Beat the boss and then go back to the smith for a nice reward.