They aren’t part of the regular soulforge rotation but some of them did show up in forge briefly last year. I crafted some at that time. Maybe there will be another limited forge period at some point in the future, now that a few more are released. But it will be up to devs to add them manually again or not
Also there was that one battlecrasher event giving copies of the Devil around Halloween.
But yes the only place they’re always available is the vault