User blog comment:CrazyMori/Belial the Implacable/@comment-3974211-20130310012223/@comment-5859769-20130310013733

It's implied that when either Malzahar or Kassadin interacted with Icathia, they disrupted his link with the Void, and the only way for him to regain a semblance of his abilities seems to be to stay in close proximity of someone who's interacted with Icathia. While he assumed he was tracking their path across the Tempest Flats, he was actually tracking Kog'Maw's trail (the consumed nomads). This eventually led him to the Fields of Justice, and he has direct motivation to stay their to try to figure out how to regain his full control of the Void while staying close to Kassadin and Malzahar, possibly to enact revenge, despite the fact that they could care less about him and do not know why he is after them.

I might have been a bit too subtle with that though, but I didn't want the lore to run on too long haha. I might rework that if more people are confused by it.