We've recently had two D&D crossover questions and I thought I'd just take the step to turn it into a trend.

I only really know Mothra from the recent Godzilla: King of Monsters film, although I know she dates back to the 1960's. According to the MonsterVerse wiki she is 52 feet high with an 803 foot wingspan. As seen in the movie she travels great distances very fast and is nimble in the air, has sharp limbs and a stinger, can spit webbing, and is as monstrously strong as can be expected from a kaiju. She's not as durable as Godzilla himself, but if destroyed is reborn through her eggs, and "fragile" by kaiju standards isn't much of a condemnation. It's a bit hard to judge her intelligence, but I'd say it's at least on par with, say, a chimp and probably similar to human.

So what would happen if one of those weekly dimensional whoopsies landed her in Faerun?

I think a certain amount of... concern... would only be natural at the sudden appearance of a giant monster, but as seen in the film if she is attacked by tiny little humans she just traps them in webbing. If she hung around civilised areas I feel eventually a spellcaster would attempt communication. Mothra is shown to be kind and benevolent, and I could see her providing aid against some giant monster or ravaging army, or settling down as the protector of a particular area. And it could be quite a large area, given her flight speed.

I'm not hugely familiar with the setting's expanded lore, but is there some Good-aligned deity whom people might associate her with?

And how do you think she'd fare, combat-wise? Isn't an ancient dragon about 40 feet long, from snout to rump? She's bigger than that, and the D&D system just doesn't scale to the kind of damage MonsterVerse kaiju can dish out. I really can't picture a Faerun dragon smashing down a skyscraper, and certainly not casually. And her webbing was shown to be able to restrain King Ghidorah at least for a few seconds.

Now, magic is a bit of a game changer and there is no reason to assume she is particularly resistant to mind-affecting spells and the like. But in terms of sheer physical might I'd say she'd continue to be the Queen of the Monsters.

What do you think?