I was relistening to Ceremony of Opposites by Samael; I thought it holds very well the test of time and I was wondering which other band you could recommend that had the same kind of sound: mid to slow-tempo, head-bangable groove, glorious and evil-sounding at the same time...

Thanks!

Well, maybe not exactly soooo similar to Ceremony of Opposites, but I would clearly recommend 'Clouds' by Tiamat, 'A Dead Poem' by Rotting Christ and 'Ophidian Wheel' by Septicflesh. These are all slower, groovier and deeper versions of black/death metal with a subtle gothic flavor, the best combination you can have for your money!

Thanks! Alas, none of them are a good match.

SF, it's goofy to my ears, owing to their gothic plastic kit that I can't stand.

RC lack the evil side,the whole "malevolent" vibe samael have; it's far too rock'n roll. but good in it's own right.

Tiamat, I could never get into their music for whatever reason - the singer for one, and the kind of broken pace they have...

Have you ever heard of Pandemonium from Poland? Their album The Ancient Catatonia might come close.
https://www.youtube.com/watch?v=1e2McrDKHpg

The follow-up The Zonei is more like later Samael