There's a reason that here on Metal Storm we have "Suomi metal" as a genre tag, something that's pretty much only found as a descriptor here. Marianas Rest might not completely fit the bill, hence why they're not (at least not now) tagged as such. They do hit a lot of the boxes though. First, and the most important technicality, is that they're from Finland. Good luck finding a Suomi metal band that isn't from Finland, weird and self-enforcing as that definition is. But the rest is nuance. A lot of elements borrowed from extreme metal, especially from death metal, without really being extreme, leading to a melodic death metal that is fully swallowed by melancholy.
So this combination of sorrowful melodies with low growls and cleaner sections, especially in the chorus, is instantly going to bring up images of Sentenced, Insomnium, Wolfheart, Swallow The Sun and the like. That "you'll know it when you hear it" that instantly makes it make sense that Marianas Rest are from Finland. You can use a lot of similar words to "melancholic" to describe the music, from desolate to gloomy to sorrowful, and I could pull out more from a thesaurus, but I hammered the point that these are expected from this sound and Marianas Rest are no different, which would make it so that their music stands out less. But one word from that same field of downer words that I haven't mentioned is "bereavement".
See, bereavement is a more specific kind of grief that follows the loss of a loved one. From its more complex phonetics to the increased specificity of its meaning, to how it ties to the cover art, I don't even really have to pay much attention to The Bereaved to associate those downer feelings with a more specific sentiment. Bereavement. There's a lot of heavy lifting done by the fact that the listening experience with all its emotional impact is contextualized as such, because this brand of melodic doom/death metal is really efficient at being emotionally impactful but has the pitfall of lack of specificity.
Of course, Marianas Rest do more than just use a clever word to contextualize the listening experience in a way that probably does more for me than for the average listener, and for a band that plays melodic doom/death metal, the "melodic" part is of essence here. The Bereaved does start with some chanting that sounds almost liturgical, that vibe only strengthened by the organ that follows. The guitars are responsible for half this album's earworms, but there's a lot to like about how the album's doomier side benefits from the keyboards and the choir, as well as the other elements that break apart from the usual metal soundscape, the the orchestral intro to the album's closer.
I find The Bereaved to do just enough to stand out, but also having a lot of its sound sticking very close to a recognizable and established one, but one that is very frictionless and easy to enjoy.