Ancient Near Eastern Monsters (with Serpentine, Reptilian and Dragonic themes)

[Icelander]

I require suggestions of monsters, both monsters which already exist in D&D (for conversion) and simply mythological ones that I can stat in GURPS. They should be serpentine, lizard-like or dragonic, ideally something blasphemously infused with serpentine elements.

The PCs have already met a snake-like hydra, a thessalmera (chimera with extra snake heads), thessalhydra (ditto for hydra) and about a thousand snakes. They are now examining a hatchery of some sort, where there are several dozen eggs from reptilian beings. This hatchery is located next to a marvelously verdant magical tree and a deep pool of water and everything seems to grow at a very healthy pace, especially considering the lack of sunlight or any nutrients which don't come from the pool or the tree itself.

These are eggs from hydras, huge snakes, carnivorous lizards and other similar monsters. Eggs from what other monsters ought there be there?

What other monsters might the PCs encounter when they crawl through a tunnel away from this place, to find the lost temple?

Background
A party of courageous PCs and their NPC allies are questing for a lost temple, as one does, below the ancient city of Unthalass in a wartorn land based on Mesopotamia.* They've heard rumours of a mysterious 'Belit emuqtu' ('Wise Lady'), also known (though rarely spoken of unless with trusted friends) as the 'Sarratum sanaqi' ('Queen of Tortures'), and run into her servants, who raid the surface world for slaves and take them into Tamtuthalass, the thriving undercity below Unthalass, and onward to further depths.

The PCs showed commendable restraint in ignoring almost all opportunities to get side-tracked from their quest for the lost temple of Su'en and refused stoutly to get involved in the criminal politics of Tamtuthalass. They did hear sufficient rumours to theorise** that whoever was running the slaver gangs was using very old legends and myths of the Queen of the Underworld, Ereshkigal and/or the Mother of Monsters, Lamashtu/Dimmu/Lilitu, to terrorise their enemies.

Apparently, underbosses are also using mythological names or titles and spoken of as the 'children' of the Wise Lady. Their titles include Abyzou, Belit Kubu ('Lady of Stillbirth'), Akhkhazu, Belit Lilitim ('Lady of the Night Spirits'), Manungal, Belit Musna ('Lady Stonesnake'), Anat-Mushus, Belit qastim ('Lady of the Bow'), Tanit-Mushussat, Rabat sirim ('Mistress of Snakes'), Ashtart-Mussatur, Belit selitim ('Lady of the Afterbirth'), Namtaru, Ba'al mutanu ('Lord of Pestilence'), Basmu-Ezzaku, Ba'al imtim ('Lord of Venom'), Zaphon-Mutu, Ba'al kashapi ('Lord of Sorcerers'), Marerru, Ba'al rabisu ('Lord of Takers') and others.

There is also a cult of Tiamat, whose modern faith focuses mainly on dragons, but who is also known as the Nemesis of the Gods and in ancient times appears to have had many of the Mother of Monsters aspects that the 'Wise Lady' is claiming. From what the PCs can tell, the cult of Tiamat and the slavers claiming to serve the 'Wise Lady' are rivals who mostly hate each other, but exist in a tentative live-and-let-live relationship, at least while foreign troops are occupying Unthalass.

Most vital to the PCs' current situation are rumours of a son of the 'Wise Lady' who has rebelled against his mother and is reputed to have hidden in the ruins of an ancient abandoned temple*** under the city, where he is said to be working with a faction of the Tiamat cult, blasphemously trying to bring into existence new dragonic and serpentine beings and thus usurping the traditional role of the 'Wise Lady'.

He is usually referred to as 'Ushum-apiru' ('The Rebel Dragon') by followers of his alleged Mother, but the full name and title he now claims seems to be Kurushumgallu, Ba'al apiru ('Lord of Rebels'). One PC now has a theory that there may be a connection between this character and a mythological figure by the name of Ningishzida, a chthonic serpent god whose name translates into the 'Lord of the Good Tree', at least in light of recent events.

*Actually Unther, in the Forgotten Realms campaign setting, but that's all that important to these speculations.
**With their Expert Skill (Bardic Lore) and Theology (Untheric).
***When a fanatical worshipper of the Wise Queen tried to convince a PC (masquerading as an ally of the Tiamat cult) to find out which faction of the Tiamat cultists were aiding the Rebel Dragon, a player actually said: "No, we're going to focus on our quest, of finding the lost temple beneath the city."