By squirting milk

Sophie: "I guess I'll see if I can squeeze out something..."

You test the waters, so to say, by lightly tugging on your left nip. The time of miracles isn't over it seems, since you shoot out a respectable white jetstream of that life-giving white fluid. Much of it even reaches orbit.

Sophie: "Good golly! I've never lactated before. Meh, I suppose weirder things have happened today."

Your breasts turn out to be an endless source of milk. You shrug and chalk this off to 'more magic'.

Proceeding to go ham on the entire East Coast, Steven soon starts getting envious of your ability to flood city after city without so much as exerting yourself.

Sophie: "Do you want some of this?"

You shoot out another squirt of milk towards Steven, who happily nabs it out of air.

Steven: "Whoa, that really hit the spot! I- I..."

Sophie: "Uh, something wrong?"

Steven: "Huaargh!"

Steven ejects himself like never before. A pillar of pure cum flies straight up into the stratosphere and into outer space. But it just won't end. As Steven is **** bent over by the intense pleasure of it, his semen starts flooding the ground.

You take a few steps back trying to evade the forwards-creeping edge of the cum puddle. Looking back you can see that the two of you have grown quite a bit without noticing - his ejaculation easily reaches the Rocky Mountains. Soon enough Steven has covered the entire continent of North America under a veil of spunk hundreds of meters deep.

He finally lets up, panting heavily. He's grown at least twice as tall than you.

Sophie: "That was... exhaustive."

Steven: "Gawd that actually hurt. But there was definitely something in that milk of yours. I need a refill!"

Sophie: "You got it!"

Steven walks over the land, snuffed out of all life just moments ago, and kneels at your feet to suckle at your inexhaustible teats. You certainly seem to have some kind of a rejuvenating property - Steven is up and ready to roll after a single slurp. A few mouthfuls and he's leaking again.

He detatches to gasp for breath, and asks you something:

Steven: "Hey, if your milk does this to me, I wonder what would happen if you ate my spunk?"

Sophie: "Well we'll just have to see, don't we?"

When both of you are standing up, his knees are level with your face. Seems that your fluids have that sort of an effect on the other person. Steven has to lift you up to his drizzling tip. Not only does he taste wonderful, you witness first hand similar effects that Steven encountered.

You grow up to his chest in a matter of seconds, warranting Steven to let go of you. You grow ever more, quickly at first, but slower as your height difference begins to wane. Not only that, but your breasts are swelling with more milk.

The situation soon devolves into having 69 with you sucking his tip and him on your boobs. After only a minute or so, you are both larger in mass than the entire Earth.

Sophie: "Shucks. I would've wanted to have some fun with the other continents too..."

Steven: "We can just destroy the entire Earth now! Maybe we'll grow enough to destroy the solar system?"

There's only one shot at this, so you need to choose carefully.