Acheron

I'm assuming these guys got their name from the Greek underworld's "River of Woe," and not from Outer Planes in D&D or from the land of dark wizards that predated Hyborea in the Conan stories of Robert E. Howard. Sadly, they never toured with Styx.

This is a death/black metal band from Florida, then Pittsburgh. I don't use that slash lightly. I understand that death and black metal are two different things, and I think I've got a good grasp on the differences: death metal refers to the musical style (super fast and brutal with CookieMonster-style vocals), but black metal refers to the subject matter (usually Satanic, or chaotic evil at best). This band gives us both in varying degrees. 

The main guy from this band was originally in a Florida death metal band called Nocotumus. He has steered Acheron through many, many line-up changes, and he's also in the proliferate American death metal band, Incantatio. He's really a member of the Church of Satan, although he maybe actually broken up with them to do his own thing. He once said, "My hatred for religion and my Satanic lifestyle is[sic] the main influence of Acheron. The demented deeds of many religions are poisoning the world we live in." Hard to argue with that! So this guy's not fooling around, as his song lyrics and general imagery indicate. If you want to see them fight with a televangelist on the radio check out these 55 mins.  Trying to find out what "The Enochian Key" referred to sent me down a google-rabbit-hole of 16th-century spiritualists and magic. They seems to have a millennialist, apocalyptic bent too, particularly on 2009's The Final Conflict: Last Days of God. Their imagery is simultaneously horrifying and cartoonish. The cover of Those Who Have Risen, for example, manages to be both absurdly amateurish and the stuff of nightmares:

Only four of their dozen or so album were available streaming online, but they seem to offer an appropriate sampling. At least their compilation of early demos that they put out in 2001 was available to give an idea of how the band started off sounding like. Can it be called a demo if the recording is so rough that it's impossible to understand the words or discern the different parts? I mean, I've put some raw stuff out into the word, but this stuff is ridiculously under-produced and messy. Then again maybe it sounds best like that. Although all dark and brutal, the early demos vary some in terms of both quality and style. Only very occasionally does the Satanic mask slip a little, and it seems like kids who really liked the first Nirvana album thrashing around in the garage...but they actually predate that, so whoever influenced Nirvana: like an evil Pixies? Maybe The Melvins? Such later-day influences seem to be confirmed when later in their long career the band ventures into sounds and styles reminiscent of Pantera or Hatebreed, although in actuality they probably eat bands like that for breakfast. Every now and then they drop in some organ or synths, maybe a gong or bells. They are occasional spoken word interludes too. All that helps break-up what might otherwise be unendurable brutality.  

After a brief split-up they return in 2014 with Kult des Hasses. It's not less brutal, but somehow a bit more mainstream - or at least mainstream for underground metal. They remain consistently dark and aggressive. In some ways, the beefed up production makes it an even heavier album. Some call it their best, but undoubtedly others appreciated the rawer earlier stuff more. It still gets crazy fast at points. 

While I can usually get into seeing any band like this live, I'm not really familiar with this particular niche of the diverse metal scene and can't identify any of the "Related Artists" associated with this band. The only song I knew before listening to their discography here and now was the great song "Evil Dead," which appears on the death and black metal compilation A Tribute To Hell: Satanic Rites.  Despite the slow opening and lengthy guitar solo, this number chugs along at an excellent fast pace. Without the guttural grunting for vocals it probably could have appealed to a broader metal audience, but whatever - it works great. Turns out that's a Death cover song. Yea, they do sound like Death sometimes! Plus: Florida; that's apparently where this stuff comes from.  

This pretty much sums it up:

It would appear they know what they are doing- and do it well. Recommended for any fans of extreme music. Explicitly anti-Christians to the front of the line.