Slayer, like say Metallica and Megadeth, rose to fame (or infamy) through a natural succession of gradually developing albums. All three started with debuts that were raw and unpolished, some might say a bit naïve (but groundbreaking none the less), had transitional follow ups before finding the band defining sound on the third outings. And with all 3 bands I find the transitional albums the best - namely Ride The Lightning, Peace Sells and Hell Awaits.
In terms of progression Hell Awaits ditches the Turbo charged Priest leanings of the debut Show No Mercy but it importantly hasn't yet mastered the technical thrash supremacy of the brutal follow up, Reign In Blood. What really marks it out from these other 2 albums is that it is really quite a disturbing album, in a really good horror film sort of way -this was Slayer at their most EVIL, sinister and, yes, unique. The oddly comic book and barren artwork, the backward intro to the Title Track, the uncompromising pace that simply never lets up from the minute Hell Awaits kicks fully into gear, the demonic vocals which are not quite in the forefront of the mix and the totally gonzoid lyrics (Necrophiliac..., say no more) all mark this out as a pretty deranged piece of work. Sound wise, the guitars attack and buzz like chainsaws, the vocals border on the sound not dissimilar to a pig being butchered and the drumming is totally unrelenting in its ferocity - if Slayer couldn't play their instruments or were not totally committed to their ART this would be awful but the sheer class that has carried them for 30 odd years oozes out of every song.
This is not for the faint hearted.