Lyric meaning question in Viva La Vida

[ArrMatey]

I was listening to the Coldplay tune ‘Viva La Vida’ this morning, and something about it bugged me. The lyrical phrase in the chorus:

“Be my mirror, my sword and shield,
My missionaries in a foreign field.”

Okay, missionaries I get, and the sword-and-shield implication thereof. Be my mirror? I’m not sure exactly what that’s supposed to imply. Any ideas out there? For some reason it’s bugging me a lot more than it should.

[Labrador_Deceiver]

I’m still trying to figure out what a Roman Cavalry Choir is supposed to be.

[Uosdwis_R.Dewoh]

Be my mirror = Be like me. Project my will to others. Embrace my cause as yours.

[ArrMatey]

Ah, okay, that actually makes a whole bunch of sense now. Thanks, Uosdwis!

[Uosdwis_R.Dewoh]

No problem.