Opeth rarities

aside from demos from the early years, no not really that anyone knows of or that hasn't already been released as bonus tracks
 
I believe there's also a rare demo of Opeth jamming some jazz improvisations with Anothor.
 
Well, the only rare thing I know is the Apostle In Triumph demo. At least, I don't know if it ever was a real demo, as I've never heard of it. I found it on the internet once, it has two sections of The Apostle In Triumph played in some kind of rehearsal room or something. You can hear Mike sing the outro piece, so I guess it's real.