Cross the Styx

Sinister's first two albums are must-haves for any death metal freak. They provide perfect music for headbanging and actually wrote really intelligent music early on in their career.
The main influence I can pick up on with this album is Possessed. This is especially evident in the use of choppy riffs (see the first riff off of the title track, it sounds quite similar to "Seven Churches") and semi-thrash riffs, albeit on here they are played at lightening speed. You'll notice a lot of blasting parts that seem almost like grindcore, but they always bring back a catchier riff so you don't get bored out of your mind. The solos are not thought-out masterpieces, but frantic explosions of notes.
Vocals are a definate strength on here. Mike was a very strong element in Sinister, and I don't think they've put out albums as strong as the stuff Mike did with them (except Bastard Saints, but I heard that it blows goats, so I never bothered picking it up). He's got a really deep and strong growl, and constantly spews out lyrics about the occult. I really wish they would have kept up with this on later releases.
Mercyless, Pestilence, and Death took the Possessed influence in their own ways, and so does Sinister. Whereas those bands went sort of progressive, each in respective degrees of greatness (Pestilence and Death) or suckitude (listen to the latest mall-core offering of Mercyless), Sinister enjoyed the full on mayhem of those crazy riffs and evil feelings.
This is better than ANYTHING Vader has ever put out, and is easily on par with Morbid Angel. Heavy. Twisted. Blasting.