Maybe he's made a bad deal with a devil or somesuch. Like he's been promised the throne if he does a favour first, and as soon as he signs the contract something starts to grow in his belly. Unfortunately, devilspawn grows at a glacial pace by mortal standards. Even with his figure, he doesn't start to show until his first grey hair shows up. And as his belly grows heavier, the king's mind grows weaker, and more paperwork is piled onto the advisor's desk.
By the time he's round and ripe, his beard is white, as is the king's. His water breaks as the king collapses in his quarters. He labours as the king lies on his deathbed. Soon the deal will be done, the king will have died of natural causes and the advisor—weak from the years of strain and the days of labour—will finally be free to ascend the throne, no heirs to stop him.
He's realised this, of course, but the devil wastes no opportunity to rub it in, perched languidly in the air a few feet over the advisor's sweating, labouring body, stuck in bed. Every now and again, a fire-red tail flicks painfully against the taut skin of his visibly contracting belly. Twice now, the devil's burning hot hand has cupped the very underside, not-so-gently jiggling it as if weighing a melon at a marketstall.
The advisor curses him at every touch, and at every contraction, calling him a dirty liar and a conman. All these years he's carried this burden around, calling on the devil to undo the deal, and only now he's old and weak will he finally get his way. What was the point?
Mock-dejected, the devil offers his sincerest mea culpa, and a new deal; the advisor will be young and strong again, and occupy a position more elevated than any mortal could imagine. In fact, only the devil himself would be above him.
Delirious from pain and rage, chest working like a bellows to catch up between contractions, the advisor watches the devil extend a hand down to him just as another contractions starts. Desperate, wanting the pain to be over, wanting the reward he's owed, the advisor grabs the hand and shakes it as vigorously as his current condition allows.
A month later, the devil lounges on an unimaginably luxurious four-poster in his palace in hell, glass of wine in hand, and watches his newest consort catch his breath.
The advisor was young again, oh yes! Fitter and more handsome than he remembered ever being, too. And very few mortals had ever even seen the devil's palace, much less set foot in its highest tower. He'd gotten his wish, in a way. What he failed to predict in the throes of labour was that his new position would be in the devil's bed, underneath him, in fact, getting fucked over and over at his 'husband's' whim.
On the whole, he had little to complain about, screaming in blind pleasure whenever the devil took him. And his new demon-form did at least keep pace with the hells. Unfortunately, it was also much more fertile than his human body had been. These two facts combined meant that there was already a lively brood of devilspawn writhing visibly under the skin of his obscenely round belly.
Something told him he'd be giving birth infinitely earlier than the first time, and swelling up again not long after. Oh well, he thought, (as the devil approvingly patted his belly, like he was sizing up a horse for auction) at least there was no more paperwork to do.
