Been a long-time fan of this style and while I do enjoy many of the full-length works from the bands mentioned above, I've always been partial to the earliest recordings. Those old demos and EP's, as unrefined as they were, genuinely captured that ancient feeling and cryptic atmosphere that helped shape the Greek death metal sound.
Horrified in particular recorded two EP's very early in their career that in my opinion overshadow their debut album and any subsequent material I've heard from them.
The earliest incarnation of On Thorns I Lay, Paralysis, released a 3 track demo in 1992 that is one of my absolute favorites in this style and I'm proud to own an original copy. The music borders on doom with how the tempo crawls but it perfectly embodies that raw, dark Mediterranean sound - something that the band wasn't able to reproduce effectively on later recordings.
I actually enjoy Obsecration's debut CD as much as their pre-1996 material as the band didn't stray far from their original sound in terms of songwriting and production. The same can be said for Selefice although their one and only album was released only a couple years after the 1991 demo.
There's an old Israeli band called Morgue who I remember seeing on trader lists but never actually heard until recently. They put out a demo in 1992 that is a dead ringer for your traditional Athens recording in this vein. The band has a YouTube channel where they have uploaded it.
Vorphalack released an excellent EP on Molon Lave in 1993 before shifting to some boring black metal, though the review I read from autothrall wasn't very favorable. Might have to write my own as a point-counterpoint. Speaking of bands that turned to black metal, Italy's Necromass recorded a very solid demo tape in 1992 under the name Dark Lust that is worth hearing if you're into the classic Greek stuff.
Another one worth mentioning is Dismaed from Central Macedonia whose
Messages from the Place of the Dead demo is more of a "brutal" take on this style with its sheer ferocity. Sadly it appears that it was their final release before the eventual break-up. I would have liked to hear more from them were they to have continued on the same path.
France's Catacomb is a mandatory listen. Unparalleled atmosphere with some Lovecraft lyrics to back it up. There are 2 anthology CD's out there that compile their early works. Highly recommended band.
The classic Greek influence even made it oversees to the US... Here's a couple obscure examples from the mid 90's. Cheers to Helvede for posting about Sacrofire in another thread some years ago.
Sacrofire:
https://www.youtube.com/watch?v=pSuvMojUPncEver Dark:
https://www.youtube.com/watch?v=-F6r0qdpY4U