He changes in midair. Now he is humanish sparkly Milan with glorious sparkly silver wings and lovely sparkly silver tail and shining silver dragon eyes (he glimpsed their reflection in the lake and adored them) and he is just a little taller than he used to be, but not that much, and flying with wings continues to be so much fun. Redesigning his clothes on the fly (heh) to fit the wings and tail was kind of hard, but he thinks he did okay.
Kithabel looks at him for about six seconds, and then she makes a "fuck it" gesture and kisses him.
So, this is technically a public place. Kithabel does not remodel the Milliways backyard, because she has installed some basic control of her omnipotence.
Instead: now they are in her Milliways room.
And still with the kissing!
Later:
"So are you going to settle for me being omnipotent to go overthrow your gods or do you want to ramp up on your own, I tried giving you some of my infinite momentum and apparently that is one thing I still can't do."
"I think I still want to ramp up on my own!" he says. "I mean, why not have multiple outrageously powerful sorcerers to throw at the problem, you know? I'm not in a huge hurry."
"Thanks. Although in a pinch of course I'm content to just park myself by a nice mountain and rearrange the scenery in amusing ways. ...Hmm, I should definitely try turning myself into a vampire again a bunch of times, I want the boost."
"Since we can get doors whenever we want maybe we should solve problems in other worlds instead of going home? Another sorcerer at home will happily take the territory and my world is pretty nice in the grand scheme of things."
"Sure. The Wild Magic seemed eager for omnipotent allies, should we ask that nice unicorn if his world wants a visit?"
"All right, I'm going to try turning again first, though."
He demands of the world that some vampire venom appear in his bloodstream.
"Ow," he says, blinking. "Okay then! I'm going to guess that was my healing power deciding that if I insist on turning into a vampire again I'd better get it over with right quick."
"I mean, I'm fine now, but I think I'd like to space out how often I do that."