I'm the author from the Sempiternal Esoterica blog. Found this thread from my referrals

Anyway, the rip provided by ImNotRussian is indeed the correct rip. Around the time I uncovered this, I had made a lot of requests on other sites and
XUXL from Yappy LOCKJAW uploaded the promo, however it was ripped too fast, resulting in sped-up songs. It didn't affect it much, but made the release sound higher-pitched than it was originally meant to be.
I acquired the proper rip from a tape-trading friend.
I have also been in contact with Jurgen Hajek for several years through Facebook and email, and while he no longer has a copy of the promo, he has confirmed that this is how the promo was meant to sound.
He also sent me a 1994 rehearsal which has a few new songs and some re-recorded tracks from the LP. You can find it
here.
I am in contact with Hannes as well, but he doesn't check his mail that much, so the information gathering is going slowly. There may be even more unreleased material, mostly unfinished riffs, so keep an eye out!