Darkness and especially atmosphere are the fucking defining aspects of that album.
And they aren't the defining aspects of Slumber? As well as its bassy rhythmic heaviness.
I don't consider much death metal to be dark, and Psychostsia is definitely not an an example of dark death metal imo. Slumber has this mystical atmosphere and aura about it that I just don't hear in the Adramelech album. That album to me just sounds like a collection of really cool riffs, hence why Burgerboy likes it.
I just finished listening to it and the riffing is consistently weirder throughout it. On first pass, there was nothing as conservative on the Adramelech album as, say, songs like Dead Soul or The Forlorn, which rely mostly on chunky power chord riffs and grooves that could have come out of Florida circa 1988.
Obviously it's weirder, that's why it's also compared to Demilich a lot. It's like a middle ground between Demigod and Demilich, but it has never done as much for me as either of those two.
I've really fallen out of touch with the style in recent years. I can't really be bothered to listen to any of it anymore but if I was comprising a list Demigod, Demilich, and Rippikoulu would definitely be my top 3. I'd also probably list early Amorphis, Convulse, Sentenced, and then stuff like Cartilage, Funebre, Mordicus, and Adramelech would be in the lower half of my top 10. It's a great album and stuff, but it's really just a pale shadow compared to that Demigod album.
I'd have to disagree with TB here. I'm in the camp that Slumber is darker and more atmospheric than Psychostasia. I
Mordicus