Mmm I think that RJ comment on this, both entities are equal but opposit. Just like the true power and the one power. If you put both in contact they seems to absord one an other.

Also the creator has already put in place mesure to compensate the power of the DO, the wheel, Tavern (I know the spelling is not right) and the Dragon.

Since both are opposit, one want to contrôle the other give a "form" of free choice. You always have the choice to see all your loves one die.

Also if both force meet in battle, there will be no winner no loser the struggle will never end and all creation will be doom.

I might add that the DO is not in "prison". It is more that création is walled in...