Another thing to worry about is if Thomas's hunger reaches his father's level, and he becomes capable of killing with just a kiss.  Even trying to release him in a controlled environment might get ugly if his demon is in charge and is that dangerous.

I still think there's a chance Harry develops something to store Wamp power, even at a significant loss, to let Thomas nurse back to health.  Especially with Lara's help.

There was a WOJ that there's a way for one practitioner to consume another's power ("and it's horrible").

I don't see Harry doing that to himself.  Not our Harry, at least.  And the wording made it sound more like they'd be merging from two to one, rather than stealing power like the Nightmare did.

I might be missing something in your analogy, but my point is that Harry was corrupted by his use of black magic. If black magic corruption is Outsider corruption, and Harry is immune from black magic corruption, then Harry can't be corrupted by his use of black magic, except in the mundane real world sense that bad acts corrupt a person.

My take is that Harry is immune specifically to outsider influence and corruption.  He's clearly affected by it, as the third eye junkie could see the stain left by Behind. And Harry seemed aware of it, which could imply others like Eb saw it and told him, since he's never soulgazed himself.

I would consider it more like a scar or stain, but one that doesn't get worse over time. I'm not sure there's an exact correlation with the port analogy.

The closest I can think of is black magic puts a hole in a steel shield, and Outsider corruption is rust that slowly degrades the metal until it's weakened and compromised.  Being a Starborn, Harry's shield has some extra materials included (nickel and chromium) that make it rust-proof.

So maybe he still gets the dent or hole from black magic, and it's visible, but it's not as bad as what others would deal with.

Tulpa!Harry conjured by conjuritis and reality disruption would be one of methods to kill Rudolph I'd not be opposed of.

Or even better Dresden having to save Rudolph from tulpa :3
Salt those wounds Jim, salt them.

And then when Dresden is kidnapped by Mirror!Harry - Harry at first is like - WTF again!

Doing both back to back might be too much or too similar, but I think JB could pull it off. Especially if the first helped him learn about himself, and the second helped him see just how good he is. 

Kind of like his ghosts of what he could be, and what he could have been. 

I'm lost on the subtlety of the difference or purpose of this tulpa then?
I've long figured in MM one of two things are going to happen

(click to show/hide)

either Harry consumes MM harry, or vice versa... MM harry consumes our Harry, but like in the Woj about what would happen if Goodman became Harry to a molecule, they're would effectively be two Harry's. I think MM and Harry Prime will balance each other out or Prime will be the stronger. Idk, everything has a balance but not all balances are seperated like the fae queens. DR needing to be made of beauty to balance the ugly, MS hanging around MW just because that's how they balance.. even Rashid.. I think his pure spirit, the laughing giggling man, contains horrendous outside monstrosities within it. So afterwards Harry won't need a balance, he is balance in action.

I don't know what you mean by consuming mirror Harry.  They're both going to be humans, presumably, with different flavors of power.  Humans don't really consume each other?

I picture mirror Harry being human with selfish motivations. I picture tulpa Harry being almost beastial, with Id's lack of empathy and the Winter Mantle's ferocity.

Imagine an iced over Harry that's gone full Winter, who's only goal is to defeat Harry's (and its own) fears by killing everything that threatens them.

Harry has issues with Marcone? Tulparry goes after him, jeopardizing their truce in the process.

Harry has trust issues with Mab? Tulparry tries to kill her to free Molly.

It'd be like the Nightmare all over again, only instead of a Kravos-based monster using Harry's intellect and strategy against him, it'd be using it to enact what he's always wanted to do, but has always been too afraid to do, for one reason or another.

As TCF shared here, the next book might not be Mirror Mirror, but instead a book spanning the year between BG and the wedding, where Harry deals with his trauma and completes some sort of therapy.

Thinking about what a villain for such a book might be, I realized that BG kind of set up a scenario where Harry might create his own enemy.

• Per Bob, tulpas might have been generated in BG through collective fear and chaotic power. Tulpas are beings created from strong emotions, feelings, and thoughts. In Supernatural, a shared belief in something created that thing in the form of a tulpa.
• Harry is suffering from conjuritis, where his thoughts are manifested using ectoplasm.
• Harry's had a ton of mental trauma, to the point that he's going to have a book dedicated to it.
• Harry's more powerful than most wizards his age, and conjuritis is rare at his age, possibly to the point to the effects might not well be known.

So, let's speculate that Harry is going to have a nervous breakdown, and his conjuritis is going to create a tulpa from his power and fear.

What tulpa would you want to see created, and what would it do?

Personally, I'd want it to be his Id self. Rather than being something attacking him, I'd want it to watch his deepest fears, literally.  I'd want it to be a version of him that gives in to its desires and tries to kill things that Harry wouldn't (Mab, Marcone, Rudolph, ghouls, etc) in order to make Harry safer.

It'd need to not be evil, per se, because that would be saved for the mirror mirror version.  And I think if they were similar enough but different enough, it could be done well, to the point that Harry having faced his own fears and issues in this next book would help him deal with the mirror situation better.

you know who'd be funny? Eldest Gruff. He was noticably absent to me. I figured since Titania refused to show she'd send him as her... Well basically as her Leah. But if he was more obligated as a member of her accords then he'd have to wear that mask. He's a hunter but won't attend the wild hunt? Maybe EK takes precedence there too? It seems to appear as his main power source in DB. That... That could be a joke told to Harry for him to figure out actually. Mentioning both of them in the same attendence. I wouldn't even put it past Kringle to invite him knowing he'd have to find a way to politely decline as some kinda fae game.
*Am I right in thinking they've never appeared on screen together?

Eldy Gru and Erl both attended Harry's birthday party at Arctis Tor, didn't they? Erl invited him hunting, if I recall.