Behind the Black Door is the first demo release from the legendary Swedish band known as Merciless. Released in the summer of 1987, this recording possesses a much different sound than what the band would develop on their following works. This is a rather important demo, as it bears more of a primitive Death Meal vibe, predating such bands as Entombed, Dismember, Unleashed, etc. Even Grave (at this point, known as Corpse), had not moved very far from their Thrash Metal roots. This release is not the highest quality among the band's output, but it established Merciless as a force to be reckoned with.
As previously stated, this material is much more Death Metal-oriented than Realm of the Dark or The Awakening, though still possessing hints of Thrash. The song structures are a bit more straightforward, at times, and the overall tone is more ominous. One of the major differences between this and the later efforts is the vocal approach. The original vocalist utilized a deeper sound, though still kind of hoarse and raspy. The riffs do not have as much depth and the songwriting, in general, is more primitive. The Kreator influence that can be heard on the following releases seems to be absent, as well. The only song on here to make it onto the band's debut L.P. is "Bestial Death", which sounded much better than this.
The production is not terrible, for a demo. The bass is easier to hear than on a lot of other recordings of this nature, though the actual bass lines do not stray from the main guitar riffs. The vocals are at an acceptable level, and the drums are just slightly higher than needed. In terms of quality, this is superior to Corpse's Black Dawn demo, but not as good as Into the Abyss, by Poison.
The first Merciless demo is rather uneventful. Behind the Black Door was, probably, more impressive at the time it was released, considering the fact that it would have stood out more back then. Listening to it now, it comes off as sort of bland and uninspired. There were plenty of other bands, in the underground, that were miles ahead of this. It may have been one of the earliest Death Metal releases to come out of Sweden, but Merciless would go on to do much more.