Monstrous Humanoid for the gladiator lizards, I guess. If you want to stat up egg guy, I could see a Native Outsider.
I still think he's a different species. Does that work for you?
Hmmmph, a dice off could perhaps be useful. I don't really like Outsider for the gladiator lizards because they don't really seem to exemplify anything.
How about a compromise? Make the lizards Monstrous Humanoid (extraplanar). Make Egg Guy a hazard of some kind, so we don't need to worry about the type. Clearly, based on the description in the story, he's summoned or magically manifested the lizards, so I think extraplanar makes sense. How's that?
Or, if we want to go really weird, we could make the gladiator lizards something like the astral figments (can't believe we did those all the way back in 2009!), so they're really generated by Egg Guy's imagination.
Not sure that I buy "sharp-edged stony deadliness" as the sort of philosophy or elemental essence that an Outsider is supposed to be about.
Any chance I can get you to agree to make the Bleak Ones and Gladiator Lizards separate species even if related? I still think that the destruction of the lizards when Egg Guy is killed means they're not the same species but something magically summoned or created (oooh, maybe the Lizards are Constructs!). And we know Bleak ones can project their image over long distances, so they must have mental or magical powers.
Bleak One is ok. But I'll probably still refer to them as Egg Guys in private.
I'd be ok with having the Egg Guy (see, there I go) as a Native Outsider. But even with your head-canon, I don't think the Lizards need to be the same type. Maybe the Bleak Ones feed on psychic pain of dying sentients, and the Gladiator Lizards are just monsters they recruit to kill people. Any chance you'd go with Monstrous Humanoid for the Lizards on that basis? I'm ok with the extraplanar subtype if you want.