Looks good to me!
Is there anything else much to change compared to the monarch, other than HD and possibly abilities? Damage and size are the same.
Yes, let's definitely stat up the crown!
So... it seems like the only thing we want to add to a generic Master Scorpion is control over scorpions, yes?
I like the attracting and controlling scorpions bit, but I think the enlargement probably ought to be a feature of the crown. At least, that's how I read the text you posted. You can convince me otherwise, though.![]()
It's just that the original text really makes it sound like an effect of the curse/crown. I think I'd rather assume that most monarch/master scorpions are naturally occurring (or perhaps bred from the original cursed ones), with the masters perhaps being special specimens, like flinds are to gnolls. The other option, of course, is to make the master unique, which I think is the case in the original adventure.
Yes, let's definitely give it an ability to attract and control scorpions. Are you thinking of a summoning type power? Or something similar to what I think we gave the master bone tyrants?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.