Aatrox's Lore Snippet: Conquer or Destroy?

On Aatrox's new lore snippet, it says he "once threatened to destroy Runeterra" and now seeks "total obliteration."

Didn't the Darkin originally invade Runeterra to conquer it? So they could get all the magic that Runeterrans were using for themselves? How can they do that if they completely destroy the planet that the magic's on?

I mean, I guess "destroy Runeterra" could be taken in the less literal sense of "kill everything on Runeterra between the Darkin and what they want." And now that the Darkin homeworld can no longer access Runeterra with the portal closed, the mission might have changed from "kill everyone and take their stuff" to "wreck a whole planet because revenge."

I just want to know what level of obliteration we're talking here.