This one was inspired by a couple of Pitchie's old riddles. Please forgive the small element of plagiarism.
Sister, dark sister,
Born in the North.
I don't wound but bring sorrow,
You kill but bring mirth.
Sister, dear sister,
Born in the South.
You signal: start battle!
I put battle out.
Sister, dark sister,
Fly swiftly away!
You go towards foe,
I to friends ride away.
Sister, dear sister,
In scarlet adorned.
You're mightier than the pen,
I'm mightier than the sword.
Please give a reasoning for your answers and try to explain as many elements as you can. Happy riddling!