"Abominations are creatures mostly born out of greed, when someone pushes his body beyond its limits, destroying it. Unlike what most creatures think, Abominations aren't only Awakened ones gone wrong.
I have fought and destroyed Abominations that spoke only gibberish, others that had no idea what had happened to them, having no concept of the mana core or world energy. They were simply born like that.
What I do know for certain, is that once an Abomination is born, there are three possible outcomes. The most common, is that the Abomination dies, either because of a prolonged lack of nourishment or because it gets killed.
They cause too much damage to go unnoticed, so humans or beasts usually hunt them down before they can learn to control their abilities. The second possibility is for the Abomination to seize enough world energy to stabilise its form and regain part of its senses.