"Either way that baby would have given him safe access to a new form until the ritual could be performed if he had possessed the mother first. He could safely move from her to the fetus as it was being born with no difficulties. But it is why he wanted Pettigrew to perform that ritual. He needed a more permanent body for his spirit. Changing host bodies had to be terrifying for him as he certainly would feel his soul trying to leave this realm and only the form he was currently possessing tying him here. He just chose to take the wrong blood for his created body."
"What's to stop him from simply jumping hosts again?"
"Death. And the fact he no longer has an anchor holding his spirit to this realm. You need to understand, Professor. Manufactured through a ritual or not, the form he's in now is his own. It will last until something destroys it. Like the basilisk venom in my blood. Just as would be the case for anyone else. That body is his just as your body is yours and my body is mine. It never held a spirit other than his own as did all the other hosts he inhabited. Including the baby he was in before the ritual had it's own soul. So this created body won't corrode early as his other hosts all did. Or at least he thought it wouldn't."
"For creation, that means that is the body of Tom Marvolo Riddle. And when that form dies, so will Tom Marvolo Riddle." Severus still didn't look convinced so Harry tried to explain better.
"When we die in our own form, we don't get the choice to simply skip to a new host form. If we did, this world would be a lot more messed up than it already is. A lot of people die before they're ready to, Professor. If body jumping was an option, don't you think those people would happily skip to a new form as well? How many of those people who were killed in the last war were actually ready to die when the Death Eater, aurors or Albus and his people killed them? If body jumping was really an option wouldn't a few of them managed it? After all, Mum wasn't the only mother leaving behind a young orphan with no one who could care for it once she died. Surely one of them had to die in a place where others were around to be possessed." Severus gave him a wry look as he admitted the simple truth of that idea.
"No, our choice is to either go on to our judgement or return here as a ghost. And since he split his soul even the option of returning in specter form is out for him. You need a full soul at the time of death to do that. The portion of his spirit he'd housed in the diary has already been dispatched. It couldn't find another form to inhabit before it was pulled onward. Probably because it's choice was either me or Ms. Weasely and to it's mind she was weak and unworthy. I was the one who killed it's former resting place. So I was too dangerous. So it got pulled onward. But that means his returning here as a ghost is out. When his created body dies he will go to his judgement like any other mortal. He has no choice."
"I see."
Harry had his doubts as to whether the man actually did see or not but he was willing to accept his statement at face value until the man said, "Still, the freed Death Eaters Fudge refuses to admit were released by him will be a problem for you. I've no doubt right now they are preoccupied with trying to keep him alive but when he does die, they'll turn their attention to you. And as is their nature they will wreak havoc trying to find you."
"And they aren't my problem. This world has aurors, Professor. Whether Fudge admits the Dark Lord freed his devoted followers or not really doesn't change their job. Now does it? Bellatrix LeStrange is a dangerous woman no matter who reportedly freed her. It's the task of the Auror force to find, apprehend and incarcerate her and her ilk again. Not mine. I refuse to continue to do a job I'm not being paid to do simply so that the people who are being paid to do it can rest on their unearned laurels bragging about how easy it was to recapture them."
"When and if those people make their move to disrupt society, I'm sure the aurors will be called upon to deal with them. Nor do I believe the people here truly expect me to do their job for them. Deal with the Dark Lord, yes. Because Albus told them that was my destiny. You know the Death Eaters have been making pests out of themselves since the World Quiditch game. Yet not one word has been heard calling for me to deal with them. Because the people believe them to be just normal people whom the aurors can easily handle." Wryly Severus had to admit that was true. No one had called for Potter to begin apprehending the escaped prisoners. Nor were they likely to until either fudge or Albus suggested it.
"Albus could suggest it Potter. Then the public would do exactly that. Demand you be brought into the Ministry and appointed the task of rounding them up for the good of the People. Because you're their Hero Boy. And Albus says it's your job to save society," he sneered.
"Albus' days of whispering ideas into people's ears as he fills their pockets with someone else's gold are over, Professor. He'll not be doing any of that anymore."
"How do you know? He's down for now, yes. Getting him booted out of the Castle has knocked him off his stride. But he is still the Chief of the Wizengamot and the Supreme Mugwump of the ICW. He is still a creditable threat to your safety."