I have lost my own challenge. much less idealistic of it's possibility, but I still killed 350 other ships before I lost everything but a Onslaught and an Eagle. CR seems to be the biggest issue here, as is Peak preformance. needing to retreat every hundred or so ship kills drains it pretty bad, and before you know it, you are on the edge of critical malfunctions.
They had 1232 ships left before I was able to start retreating, and makeing a run for my life.
The opposeing fleet covers the entire campaign map screen as far as you can see. It's... terrifying. Escape is incredibly difficult.
I lost 8 ships, and killed about 375. they had 1212 left. Pretty decent numbers!
_EDIT_
I escaped to jangala startion with only the Onslaught left. Took this picture. You can't even see the circle for how huge the fleet is, but the pop-up triggers somewhere to the bottom right of the ability UI. The map shows it, but it doesn't show how big. I'm going to attempt to find the edge of it via teleportation.
http://imgur.com/V9BQhVj_EDIT_
A quick jaunt to Asharu reveals the edge of the hoard. Makes me wish there was a hide command for the console, I think I'll go politely ask for one.
https://imgur.com/ZJQT8U9_EDIT_
The red line of an obvious pirate turns to grey as soon as you step outside it's bounds. You need to be incredibly close to see the danger, if it's not readly obvious from the size.
Still no ships within the depths of the circle.
_EDIT_
The mass is amuseing itself, destroying all the ships within it's radii with impunity. Sparks of explosions appear intermittedly as unidentified ships vanish in it's mass.
I don't know if it can move. And if so, how fast.
_LAST EDIT_
I've given up trying to see if it'll move. There is unlimited spawning within it's reach, it has no need to. Trade disruptions run rampant inside it's area.
To give you a better idea of how big it is...
https://imgur.com/AewAGWdThe only pirates you can see on that map is the challenge hoard.
Where my icon is, the small, three triangles, is where the edge of the circle is.