So I've been thinking of maybe writing a story that takes place in primative Equestria some time prior to Somnambula, involving a monster mare in an egyptian setting. I'm not too sure what I want to do. I was thinking maybe a Lamia, but I'm not too sure.

Suggestions are fine, just don't suggest Sphinx (I don't want to do a Sphinx).

Hello! What about Ammit?

Oh if I using their gods then I would recommend Sobek

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A lamia does appear appropriate, seeing that snakes seem to go well with Egypt (such as the Egyptian Cobra).

Well, if you're trying to think up a monster, there's plenty of gods that take animal forms like jackals and eagles. Scarabs are also a very common theme for Egypt. There's plenty of creatures in the Nile, like hippos and crocodiles.

I would say mummy, but that's as common as the Sphinx.

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How about Babi since he was considered a deity of the underworld.

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I like the idea of a sphinx

Classic Mummy could work too.

An Anubis-esque pony perhaps? Might be a tad plain though.

Big ones that come to mind are Ammit and Apep.

7189245 *Looks up Apep, somehow also finds information on Kebechet.*

Hmm... What if I combined the two?

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Well, here are a few Egyptian Monster Mares made by Badumsquish:

Also, there is that Egyptian Pony from the IDW comics:

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Honestly i don't know much about Egyptian monsters other then Mummies, Sphinx's, Doppelgangers, and that alligator/hippo thing that eats hearts (i can't remember its name) other then that i can't think of much, maybe a snake monster or some avatar of a deity? (i want to say scarab but i know that isn't helpful)

You know thinking about it i remember that the cthulhu mythos tended to have some connection to egyptian myth so maybe you could use that to mix things up?

if more middle-eastren monsters are allowed then i would suggest a ghoul or djinn

Edit: Oh how about amphisbaena? she is more of a greek monster but one that lives in a dessert and should fit.
she is the daughter of medusa that was born from a drop of blood that landed in the dessert, in myth she looks like a giant snake with a head and pair of legs on both side's. though a more monster girl version is found in castlevania sotn.