"Hmm. I do not think Eru could have erred in his understanding of the universe. Is it not possible that Ungoliant does come from another star, but another star in our, ah, universe?"

"Wouldn't he have seen it, if there was one?"

"Yes, but we might not have. Not all the Ainur joined in the fashioning of this world, and I don't know what the brethren we left behind for that project have achieved since."

"Oh. So they could have gone off and made other planets and filled them with other things, such as light-eating giant spiders?"

"It seems unlikely they'd have done that on purpose, but we made a few mistakes here on this world before we got the hang of it."

"...Oh?"

"Well, worlds aren't supposed to be this shape, it's actually not the one that makes them hang together best, but by the time we realized that we had everything falling in the right direction and the stars up in the sky and didn't want to crush it all and start over, and we had too much material and would have had to somehow get rid of it. Also when we introduced oxygen there was a mass extinction event. There were actually several of them."

"What shape is it? It didn't occur to me that it wouldn't be a sphere."

"It's flat."

"Oh. Yes, that would be... unconventional. And may affect my teleportation spell if I don't want to land upside-down and can't assume that 'down' means 'towards center of sphere'. How thick is it? Are there things on both sides? What shape of - flatness, is it?"

"Cylindrical disk, very thick, so things fall down properly. There's nothing on the other side as far as I know. Near the edges things behave very oddly, but everywhere else it's fine. You didn't notice? You can see that it's flat by standing at the shoreline and looking at Valinor."

"I can't see that far."

"Ah. Well, you can ask any Elf. We can't reshape it now, the process generates extraordinary amounts of heat and there are all the people living on it."

"I would imagine it would be hard to sustain in a cylinder shape, actually, I'd expect it to collapse with a great deal of fuss and seismic activity."

"Well, we used magic. It's perfectly stable, it's just not as we realized belatedly it was intended to be."

"All right. How do things behave oddly on the edges?"

"Since it's the existence of a large mass that creates the downwards force, on the edges the force is highly irregular and pulls you what feels like sideways. We tried using magic to correct this and now it just kind of shunts you to the nearest place where the pull is downward. It also warns us, so we could rescue anyone who tried and got in trouble."

"Is there anything on the sides or are they empty like the bottom? Are they solid, or seas?"

"Empty and solid, mostly very mountainous."

"If someone wanted to for some reason, could they climb around the edge?"

"I might be able to. You'd have to be much much stronger than the Eldar are."

"Huh. Well, I'll add 'irregularly shaped planet with patches for gravity and shape stability' to my list of things I need my teleport to handle." And she does that. "Was Ungoliant a person, would Eru have had to wake her up?"

"She struck me as such, yes. She might be some kind of Maia herself. I doubt Eru created a thing of that form."

"So she's like the giant spider version of a Balrog? And you don't know who she was, like, personally."

"Her mind and powers were unfamiliar to me."