Krakia?

An "invasion coming to Maple World" means a force from out comes in. That would rule out anything we have or have been hinted at thus far. It actually sounds like an Omega Expansion, to me.

Giving Hime credit for her wittiness is not something we'd normally do. Don't assume to know exactly what she meant. Also, even if you were correct. Invasion can also refer to a sudden massive attack from an outside force. Krakia attacking Masteria/NLC could just as easily be an invasion. Or from Versal for that matter, which is outside the maple world.