-2000000000 Gildar

I went in debt to about 500 gildar, and then an enemy demanded tribute, which I paid.  All of a sudden, I was over negative two billion gildar in debt.  The number never changed no matter how many turns went by, and as enemies kept demanding tribute (sometimes demanding billions of gildar), I kept paying them in "credit."  However, eventually I got to a point where the "turn" button wouldn't let me click any more so I couldn't play this out to the end.