Late game minor race exploit.
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Stardock Forums
I have used this a little before, but I have just discovered that there is NO limit on it. In the late game, go to war with a minor race, then make peace with them. Overpower them by enough that you can demand their entire treasury of 1000 to 2000, every turn for the next fifty turns. They can go as far into debt as neccessary to pay you, and you can superfuel your empire on it. The last game, I put the fundamentalists at -56,403 before I was through with them.
-Drake
~SDC~
-Drake
~SDC~