Metaphysical / Paranormal event
The other gods learn of Silvanus's and Shar's little pet projects that have resulted from the Material Plane's construction; the Feywild and Shadowfell.
Leave it to Silvanus to disobey an order! Not to mention that word got out about it, and now Shar has gone and done the same. Thank goodness Gond and Oghma have gotten some barriers up since then, but the damage is done. At first I had hope the larva would never stumble into these places, but that was too much to hope for. A realm of twilight, and a realm of shadow. Very curious how those two managed to create such perfect mirrored planes. I pity anyone that crosses paths with any creature that springs from either of these realms, honestly. With how capricious Silvanus is, I'm sure whatever creatures he's spawned there are just as troublesome.
I find it rather interesting how these portals that have appeared seem so closely tied to light. During twilight hours the frequency of these portals is much greater than at other times of day, particularly during full moons. And Shar's realm of shadow seems more easily accessible in places on the surface where light doesn't hit, and again particularly more often during the new moon phase. I can't help but wonder if Selune had something to do with this. Well, what's done is done, let's just hope none of them make the jump from those parallel planes up here to Celestia!