rmp321 ivala is shielded by her choice. at least based on tertia saying. who captured her it's not in a physical way, but more cut off her from the world and 'harvest' her power.
for the IK original invasion, they don't have any chosen back then, and they start to appear only after the skirmish in zirantia when wendis die (based on sarai talk)
so i think their ability to use or even harvest ivala's power is recent, but her imprisonment is far more ancient.
wendis said to have 'see' "two focal points around which all reality flows"
one of them is "One of them is a very orderly type. Seems like he would definitely destroy me if he could, so I tried to stay away." and this should be the anak (hoever he is, he has all different kinds of power. We need to stay well away from him.)
the other: "It's extremely obscure, I think by design. Fortunately, it doesn't seem to look in my direction much." and this should be ivala.
tanurak when reach ivala mountain he said: "The world used to be so freely flowing and easily manipulated... it's become so unpleasantly stable.../Whatever THIS is, it's a central part of the whole pattern."
this don't help us to come close the true, but there are some facts to be added to the whole.