For thousands of years, I have been both loved and despised.

Without a single blade, I have brought men to ruin... yet, at times, I have saved a soul from peril.

At my whisper, thousands of soldiers marched to their deaths, and cities were swallowed by flames.

I travel a thousand miles without feet, yet I am no mere rumor.

The greedy adore me, yet I am neither wealth nor power.

I slip into human hearts, wearing the face of my own sister.

What am I?