It's Smaugust again and with the third season of House of the Dragon teasing Baela and Alyn's relationship I stumbled upon an interesting lore tidbit from the books.
In the book lore, the two have a daughter named Laena Velaryon, and as per tradition, a dragon egg is placed in her cradle to bond with the hatchling within. However, to everyone's horror, what hatches out of the egg is not a normal dragon hatchling, but a "blind, maggot-like, wingless white wyrm" that promptly attacks its cradle-mate and injures her until Alyn finally kills it by "hacking it to pieces".
The exact nature of this "wyrm" is left unclear, with the most likely one it being just a prematurely-hatched, severely-malformed infant dragon lashing out in pain at anything in the vicinity, a mutation caused by the declining gene pool of the last few surviving dragons. However, a couple of more interesting possibilities are probable given another bit of lore given in the books about the origins of dragons and magic in Valyria.
According to some theories by historians, dragons were actually hybrid creatures created by ancient Valyrian magic using two naturally-occuring creatures in Valyria, the wyvern and the firewyrm. So it could also be that Laena's "wyrm" was a sort of "genetic throwback" to the firewyrms like how Caraxes is often theorized to be (though significantly more malformed), or perhaps it could even have been a straight-up firewyrm egg mistaken for a dragon's egg, and as they are described to have "no love for men" it merely considered its cradle-mate a potential meal rather than a companion.
Aside from drawing these three possibilities of what this "wyrm" could be I also drew some designs for the original Valyrian firewyrms and wyverns. The firewyrms, stated to be subterranean burrowers, would certainly fit the "blind", "wingless" and "pale white" descriptions of Laena's "wyrm" as a subterranean creature would have no need for eyes or pigmentation, and their fire breath likely used to help melt through solid rock as they burrow underground. The wyverns, on the other hand, are more mundane flying creatures similar to pterosaurs, though scaled rather than covered with feathers or fuzz, and having prominent brow crests that extend into horns, similar to those of Syrax or Silverwing, marking them also as throwbacks like Caraxes, but more toward the wyvern side of their ancestry.
