Forgotten heavy bands from late 60's to early 70's

Yes to Jade Warrior!!

The name will not shock anyone, but Deep Purple. I only mention this because I dusted off/played their Shades of Deep Purple album last night. This is their lineup w/Nick Simper on bass, and Rod Evans on vocals. Although Jon's keyboards are easily distinguishable, it is very different than the mk. II lineup.
I found this to be an interesting listen. They do a version of I'm So Glad, which of course makes one think of CREAM. It's actually a Skip James tune, which I learned while reading the album cover. I really have to be in the mood for Made in Japan..., but Shades less so.

The new Small Faces reissues are brilliant

Iron Butterfly put out an album later in the 70's called Metamorphosis. This album was a sea change for them, different music than from their Inna-Gadda-Da-Vida days. Three of the four original members remained but they added two guitarists, one of whom played slide guitar. It retains the heavy sound but branches out in style and playing. The album has a picture of mountains with two coffins on one of the mountains.

I wouldn't call them forgotten (maybe not so well known in the US), but I have to mention Hawkwind. Space Ritual is the ultimate heavy psychedelic album.