The first clear influence for Stone Breath seems to be earlier In Gowan Ring, which I generally prefer to later IGR so good move there
Of those yet to be mentioned here or in the
Psyche Volk thread (which was admittedly more the noodling hairies than the robin hood tights), I'd suggest Richard Skelton's A Broken Consort project, which at times very slightly reminds of the more instrumental Stone Breath, though all of his projects are worthy of investigation:
https://aeolian.bandcamp.com/musicFor a slightly doomier vibe, perhaps a bit more nature-y than tights, some of the things on Glass Throat Recordings could qualify. Alethes, Fearthainne, The Elemental Chrysalis, others.
https://glassthroatrecordings.bandcamp.com/Zeno mentioned Little Somebody Records, and for the tights wibe I'd go with Green Mistletoe, which is almost exactly how you'd expect them to sound with a name like that.
Far Black Furlong finds Richard Moult-y piano drone delivered by set of performers with robin hood tights squeezing their collective nuts off. Very delicate squeezing out of the choicest sounds
http://music.farblackfurlong.com/album/the-east-roomI'm not the world's biggest Sol Invictus fan, though they do have their moments. I do like Grey Force Wakeford. Still suffers slightly from the huge reverb with which Wakeford saturates most of his recent work. Duo Noir's Sintra (with Andrew King) is also pretty great. "Black Crusade" is a great booze-it-up-'n-sing-along ditty.
Only vaguely related, but with a slight Appalachian folk connect plus very good- Cye Wood And Lisa Gerrard - The Trail Of Genghis Khan.