Interpretation - this song strikes me as being about how addiction or self satisfying behavior (Narcissus) will f**k up your life.
"Deep Six" is slang for smoking drugs quickly, six feet deep is where smoking drugs will get you.
He mentions how a stranger came inside his mind - which is liken to feeling out of control the way addicts do.
Then talks about what hes lost - lead artillery, wax wings - limited freedom, broken down defenses.
Maybe I'm just interpreting it like this because I'm in recovery from addiction.