First, I approve of this message
Why exterminate?
We can assume CE started as gem mining outpost for nobles in the south, something with a few unicorns as detectors and a lot of earth ponies as labour. Over time, it accumulated enough wealth to become a state in its own right, crystal heart being just defence system made by old unicorns.
Also, come to think of it, isn't Celestia's line 'King Sombra, a unicorn whose heart was black as night' a stealth insult at her sister?
At M.A./M.Sc. level, the buzzing is twice as loud. Hurr