So, my context for comparison is basically
this.
And I'm not disappointed.
There's quibbles, of course. Like how this black dragon doesn't feel like a
black dragon to me (where's the disease, the insects, the rot, the corruption? The lair gets at it a little bit, but a black dragon to me is a dragon of the PLAGUE, not a dragon of aggressive dampness!). But the good on this is far outweighed by the bad.
I like that it breaks the action economy. This goes with my article's idea of "triggered" actions. I kind of like triggers better than just a list of things personally (they're easier to keep track of and can involve more strategy), but a list of actions is fine in concept. The lair adds to this, I think.
I like the link to the lair. A black dragon doesn't just sleep in swamps, the places where it chooses to sleep
become swamps! This can interface with an exploration module pretty well (and I'm a little disappointed that this one doesn't!).
The idea of ignoring d20 rolls is very similar in intent to my idea of an overwhelming power dynamic. Like with the action economy solution, I'm a bigger fan of a "weaknesses" system than just an "I Win" button (easier to remember, more fun in play), but it's conceptually the same thing.
I'd prefer if it had different ways to spend that legendary d20-negating power. Auto-success sounds like a lot of fun (you made your save against the dragon's breath? Oh, wait, no you didn't!). I don't see why they can't negate attacks in general. And the d20-negating power + magic resistance seems to be overkill against magical control...but what do I know?
But I really like it. It's a great first iteration.