 The language of the aliens is actually English played back in  reverse. The original (normal) sentences can be heard throughout the  episode. The aliens first line is composed out of: "from this moment  on, you exist only" and "vulnerable points". The last aliens  dialogue is composed out of: "that there are three alternatives",  "primary test objective", "we have studies Earth from a", "has been  located", "know its vulnerable points" and "you exist only as a  convenience".