A great magical barrier was placed around the plane containing the warring dragons. This barrier could be broken, however it was enough to keep the dragon’s in. Neither entity had any desire to leave as their enemy was right at their doorstep. The barrier was just a precaution by the other gods. If one of the dragon’s could use all of his resources towards destroying the barrier, however, it would be possible for him to exit the plain. That is why the gods attemepted to make the dragon’s conflict unending; in order to prevent an attempt at destroying the barrier. If a dragon tried to destroy the barrier while his opponent still thrived he would not be able to focus enough on the barrier to destroy it, nor would he be able to fend off his opponent with the remaining resources.