When can he start helping Kithabel out on projects of meaningful size?
When can he start flying?
...Flying, not yet.
Kithabel makes a habit of doing all her sleeping in Milliways, since she can get doors at will.
...
With zero effective time spent sleeping, and a maximum mental capacity climbing steadily from seven times normal, it is not going to take him all that long until he can fly, is it. (Although becoming effortless master of all he surveys is still a frustratingly long way off.)
He can set a record. (Kithabel approached the previous record but did not break it. She will try not to grumble.)
So, he does cooperative projects with Kithabel and manages an ever-increasingly complex entourage of assorted performing objects and pushes for flight and automation and more things more things more things. As many things as he can possibly do. More things than that.
When Kithabel thinks Milan will be able to fly any day now, they go into Milliways for naps and there is someone there.
"Also! You from an Earth or not an Earth, it's fifty-fifty so far."
"Not an Earth. I'm a sorceress, he's working on it, he moved to my world because his... was dangerous," she amends from something less polite.
"Sorcering is fun. I'm not from an Earth either. Can I ask, are you human? You don't quite look it."
"Some otherworldly version thereof, I assume, it'd look different if you were the kind from home."
"I'll take your word for it. My kind look like our original selves plus sparkly complexions and red eyes."
"In addition to the aforementioned we drink blood, we have rather unfair arsenals of superpowers, and some of us get magic on top of that."
"Super speed - cognitive too - and eidetic memory and massively overkill physical strength and we can turn on a dime, all part of this complete breakfast."
"How charming. Are there any horrific disadvantages? Or even merely inconvenient ones? Also, what's the deal with the magic exactly?"
"Unquenchable thirst, we can't sleep -" She looks at their faces. "Or that's an advantage?"
"An enormous advantage. Tell us more about this unquenchable thirst. How unquenchable is it?"
"Well, you get a few moments while drinking blood but it's basically there all the time. It's not half as bad as actually turning, though, that's nasty stuff."