I managed to fix the bugs! (Also, at first I uploaded game files with test variables left in, so for a short while when you launched the game, it started you with 999/40 HP... But that too is now fixed).
Yeah, the whole idea behind that enemy is that once the fight goes on long enough for it to fire its "ultimate", it's game over. I added it in the 1.2 content update, alongisde the ancient dragons, because some players said you could get too overpowered in the end game and wanted more challenging fights :D