Armand showing up missing an eye instead of Lestat is a major clue that he is directly involved in protecting the vampire world from Akasha. Armand has a pattern, a scheme to counter the great conversion, he is not the main antagonist you're looking for in this season.
The beheading is a mean to justify the end (also a snarky revenge towards his ex-lovers with the love of his immortal life). This is as simple as that.
















