Somber 7 is the most ridiculous to find in the whole game, I'm barely into Liurnia and I have every stone but 7 and 10. 3 copies in fact of somber 9s.

What a horrible description of the volcano manner whereabouts

Don't you have better things to do with your life.

Large Fingercreepers past Giants Grave Post site of grace drop these regularly

"found on a ledge guarded by an Abductor Virgin across the bridge northwest of the Temple of Eiglay site of grace." lol instead of giving actual directions to the stone you use a path that involves a skip.

The link to mowgyn palace shows a regular smithing stone 7

I'm still trying to understand From's thought process on making this the hardest somber stone to get? Every other one is fairly easy to get to, even 8 and 9 aren't hard. It's just this one.

Farmable: the fingers at the Mountaintops near the Church of Marika

I'll post it as a top level comment: The earliest +7 you can get is in volcano manor. I beat him at rune level 1, and my dodging skills are average at best. Get yourself some bleed weapons (eg 2 uchikatanas if you started as a samurai, or metoric blade/uchikatana works too) and a few sleep pots. You can craft those with the Fevor's Cookbook (1), that can be found in limgrave. Then you'll be able to kill the godskin noble (the only boss that prevents you from getting it "legit"). He's behind the fogwall just behind the big bridge. Don't forget to upgrade your weapons to +5-6/10 before the fight, it helps. Use the sleep pots until he falls alseep, be careful that throwing a sleeping pot when he's falling asleep will wake him up (yay). Then keep hitting him until he stands up, throw some again and repeat. He has a phase transition where he begins to roll (you can't stop it), just get behind a pillar, put it rather precisely between you and him, and you're good. And btw, those sleeping pots will still be very useful when you fight the Godskin duo. After that you can get a +8/+9 in Caelid, but I guess you know that.

As of 1.06 early SSS7 (by wrong warping and/or Manor skip) isn't possible anymore