She has to. Which such a guy fighting her at any moment?

I'm lost. Why would Noah entering a mindscape unleash nightmares?

Now what would be the right scenario like, then?

Don't be a welcher, Noah.
I do wonder how the nightmare sending works though. Can Chernyl not produce another Hallowman while he's trapped in Noah's mind? This page implies sending nightmares into mindscapes isn't voluntary on Noah's part, but it seems controllable because they trapped the Hallowman. Was it random chance the Hallowman went into Noah's head? Are all of the nightmares trapped in Noah's head now if they'll only appear in the mindscapes he'll enter?

@Tom: I think he wished for the nightmares to be trapped in his mindscape. Which is why the world became safe again. He made a big sacrifice.

@Tom
Noah wished to be able to absorb the nightmares into his mindscapes. The mindcapes are likely more accurately described as hellscapes now.

@Tom: I don't think Noah meant the nightmares would be unleashed, merely that one or more would likely be waiting in any mindscape he visits and, lacking other targets, gleefully attempt to murder him. Possibly hoping to escape by doing so, possibly just because it's what they do.

@Tom I'm theory-crafting here a bit but we know Noah now sees the Hallowman in dreams. It is like a mind parasite. Something in Noah's mind keeps it chained. Yet he has dreams with nightmares produced by it that attempt to seize control of the mind.
Now I assume from what we've seen that Noah's power inserts his mind into his target's. Here I theorize this risks contagion and The HallowParasite could tap into the target's mindscape and create nightmares based on that mind, potentially worse.
I don't know if it is really true what Noah states. As far as I understood Hallowman can only create nightmares based off its' host's own; it creates out of the host's deep mind, so to say, deeper the more control it gets. I see it like like Ciel only being able to read surface thoughts as Noah keeps control over it too, Hallowman reads surface fears.
I imagjne Hallowman being able to create Nightmare Dentist as it was experienced by Noah, but unable to create Nightmare Math since he wasn't there and is not part of Noah's nightmare fuel.

He wished specifically, for the power to send Nightmares into Mindscapes. There were thousands of Nightmares active, and he sent all of them into Mindscapes. Now likely anyone in Justopia could be housing a Nightmare.

The difference between Chernyl and other people is that Chernyl made the Nightmares tangible. Regular folks without this ability won't manifest them outside of their Mindscapes, so they're just normal (relatively) Nightmares unless Noah has to engage in their Mindscapes directly.

The hosts of their own dreams seem to only take damage from outside their bodies, but Noah can take damage inside these Mindscapes.

Having these Nightmares randomly distributed amongst literally anyone has made the use of his power that much more dangerous to himself at the sacrifice of making sure everyone else is safe.

He wished specifically, for the power to send Nightmares into Mindscapes. There were thousands of Nightmares active, and he sent all of them into Mindscapes. Now likely anyone in Justopia could be housing a Nightmare.

The difference between Chernyl and other people is that Chernyl made the Nightmares tangible. Regular folks without this ability won't manifest them outside of their Mindscapes, so they're just normal (relatively) Nightmares unless Noah has to engage in their Mindscapes directly.

The hosts of their own dreams seem to only take damage from outside their bodies, but Noah can take damage inside these Mindscapes.

Having these Nightmares randomly distributed amongst literally anyone has made the use of his power that much more dangerous to himself at the sacrifice of making sure everyone else is safe.

@Tom I'm theory-crafting here a bit but we know Noah now sees the Hallowman in dreams. It is like a mind parasite. Something in Noah's mind keeps it chained. Yet he has dreams with nightmares produced by it that attempt to seize control of the mind.
Now I assume from what we've seen that Noah's power inserts his mind into his target's. Here I theorize this risks contagion and The HallowParasite could tap into the target's mindscape and create nightmares based on that mind, potentially worse.
I don't know if it is really true what Noah states. As far as I understood Hallowman can only create nightmares based off its' host's own; it creates out of the host's deep mind, so to say, deeper the more control it gets. I see it like like Ciel only being able to read surface thoughts as Noah keeps control over it too, Hallowman reads surface fears.
I imagjne Hallowman being able to create Nightmare Dentist as it was experienced by Noah, but unable to create Nightmare Math since he wasn't there and is not part of Noah's nightmare fuel.

Noah acting like this with Ciel is SO tiresome.

Little do we know, but Noah is playing the long game:
he's making all the military people think he can only talk to his power out loud

That way, if them (or someone spying on their intel) wants to capture them, all they're going to do is gag him and assume that seals away his power.