I'm guessing Mikael is also a fan of Coven's 1969 release "Witchcraft Destroys Minds and Reaps Souls". The last track is supposedly a recording of a satanic mass, and part way through, five names are chanted:
Satan! Beelzebub! Leviathan! Asmodeus! Abaddon!
I remember the last time Opeth came out here (Australia), Mikael introduced 'Deliverance' by asking the crowd to chant these names (they were the same names, and in the same order). Could be a coincidence, but unlikely.
Another slight possible reference is on the Still Life album (by the band of the same name); there's a part in the first track about 'sinking beneath the mire' or something (I can't quite remember, but I can't be bothered to put it on either). As I said, very slight, and only a possible reference, but... *shrugs*
I was also wondering if there are any Jacula fans in here? Not the greatest of bands, to be sure, but has anyone heard 'Triumphatus Sad' off 'In Cauda Semper Stat Venenum'? This has a black metal guitar sound almost FIFTEEN years before Bathory! (it was released in '69). I was blown away when I first heard it - the guitar tone/style sounds like nothing of the time, until Bathory, Celtic Frost, etc. The drums aren't blasting (of course) - they're very minimal - but the guitar?!? Wow. Makes the Sabbath debut seem a whole lot less heavy.
I recommend that anyone interested in proto-black metal check out at least that track - puts a whole new perspective on things. In fact, anyone interested in Opeth and progressive rock (ie: you guys) should check it out. The rest of the album (and subsequent albums [the main guy, Antonio Bartoccetti went on to form Antonius Rex amongst other projects]) didn't explore the sound further, at least to my knowledge. I only own the first (and only) two releases under the name of Jacula, but as I said, check out 'Triumphatus Sad'. I think you might still be able to download it on
http://www.antoniusrex.com/auditorium.htm.
Most of their other stuff is very occult-influenced (the lyrics were written in conjunction with a medium), and very heavily organ-based. There's some spoken word material, in their native Italian, English, and Latin (some of it quite chilling when in the right mood), and some female vocals. Definitely an interesting band, if not a very good one.