Hollucard
You are familiar with how magic must balance with life, yes?
Osaron is a piece of magic which has somehow gained control over itself, and ideas of its own, but it still requires the energy of life, blood, and the world around us in order to gain strength. Of course, because it also has no human mind, heart, or moral compass to impose limits on how much energy to draw, it takes everything until there is nothing left. It can give energy, as well, as it did in my world, but I don't believe it would have done so of its own accord, had I not asked for it. Makt, I think, was not a world with enough energy to satisfy it, especially with having to output energy to bring magic back into it. I was the only true source of energy in that world, but it was not, at first, strong enough to consume me.
Eventually I think it would have continued consuming until every world was just like the one I found him in. Which was a dead city entirely made of blackness and stillness. My blood brought some of it back to life, though.