Mephisto's S/T might have been my favorite first-listen experience of any album. I got into them before I had even listened to their likely influences (e.g. Angel Witch) or better bands like Adramelch, but that was my first time hearing an album with such an obscure, fantastical quality and it totally blew me away. Didn't quite hold up with repeated listens but still a sentimental fave, and the title track is still a perfect 10/10 song.
EDIT: Actually my first listen to Energetic Disassembly is a close competitor, but yeah.