I mean, for putting Zarah and Zigma from the spotlight. The gathering power could have attracted the attention of some lone maverick Scourge from under the sea. Comes out of the sea at around the same time they go to Lyra's camp, bang, zoom, taken care of in maybe a grim way. :X

Could say that, in the aftermath of the sealing, the millennium before, a fight brought a cruiser or whatever and some Scourge assets here, and they crashed on the other side of the planet, and that's where it came from.

Like I said, that's... Drastic.