Voldemort's servant did not understand Voldemort's outrage.
He only cared about his own situation.
Faced with a ring of rats that surrounded him without attacking, the young wizard was on the verge of a total breakdown. He was convinced the rats were only waiting because fear would make the flesh taste better.
"You're not eating me!"
The young wizard took a deep breath, raised his wand, and spoke the incantation. Crimson fire burst from the tip, surging outward in a violent wave.
It was extremely advanced Dark Magic, the kind many wizards would never dare attempt.
But the young wizard was panicking so badly he no longer cared.
The dreadful Fiendfyre spread like something alive, racing across the ground, climbing the trees. The rats actually stepped back a little, clearly shaken by the terrifying magic.
They squeaked at one another, sounding deeply confused.
But the young wizard could no longer hear them.
He could only hear himself screaming.
"AAAAAH!"
The fire caught his robes.
Then his arm.
Then his face.
Not everyone was qualified to control Fiendfyre.
"My lord! My lord!"
The young wizard rolled on the ground, but the fire would not go out. He threw himself toward the filthy runoff water, but that would not smother it either. The Western version of playing with fire and getting burned had just become very literal.
"No!!!"
His scream turned into a wail.
His body began to shrink in the flames, like a sheet of paper set alight, curling from the edges, blackening, collapsing into ash.
At last, it scattered into the runoff water.
From beginning to end, it took only a few seconds.
A wizard with dreams of glory, with ambitions of rising high, died without ever even leaving his name behind.
"You damned idiot!!"
Voldemort, who had still been lost in thought, was caught up in it as well. His soul burst out of the ashes.
No longer black smoke.
Now it was pale as white mist.
Thin as gauze.
It drifted through the forest air, so faint it looked as though a breeze might scatter it completely. His voice came from within the haze, hoarse and weakened to the limit.
But still furious.
"How can a grown wizard be stupid enough to lose control of Fiendfyre? You pig! You've ruined everything! You were one of Dumbledore's planted martyrs all along!"
Voldemort did not spare a single ounce of grief for his dead servant.
After finding a new way to interpret the world, he had become more convinced than ever that he was surrounded by Dumbledore's agents.
After suffering blow after blow over the last few days, this thread of Voldemort's remnant soul looked as though it could go out at any moment. Screaming, it rushed deeper into the forest in search of a new host.
Even with the threat of total soul-dissolution hanging over him, Voldemort refused to possess a rat. If he could not inhabit a magical creature, he would at least find himself the body of some normal animal.
Once the Fiendfyre had been swallowed by the fire-breathing rat, which promptly fainted and was dragged away by the others, silence returned to the forest.
The remaining rats stood in the distance, stunned.
Their mouths hung open. Their eyes were wide. Red pupils reflected the scene before them and fixed on the little pile of smoking ash on the ground.
Squeak.
One rat cried out softly. The sound dropped at the end, like a person saying, My God.
Squeak squeak.
Another answered twice, quick and sharp, as if asking, Did you see that?
Squeak squeak squeak.
A third gave three long squeaks, sounding almost like a sigh.
It was obvious the sight had deeply shaken these newly awakened rats.
A human wizard, in front of a group of warm-hearted giant rats who merely wanted to share the glory of Ian, God of All Magic, and His Chosen Vessel...
had just burned himself to death.
None of the rats understood it.
None of them respected it.
But they understood one thing more clearly than ever:
Humans were insane.
No wonder they needed Ian, God of All Magic, and His chosen one to save them.
...
Voldemort's remnant soul drifted through the forest for a long time.
At the edge of the woods he found a stag. A large one, with long antlers, standing peacefully in the moonlight and grazing.
"No time to be picky. I need to recover!"
Voldemort's remnant soul lunged like a snake bursting from the grass and drilled into the stag's body, forcing a possession that was, in truth, a very poor fit.
He had no choice.
Weakened to the point of losing his magic, Voldemort's remnant soul could not possess a human anymore. He probably could not even manage an infant now.
An animal would have to do as a temporary bridge.
Hide.
Recover strength.
Then slowly lure in some unlucky passerby.
Humiliated, Voldemort laid out the plan in his mind.
As he possessed the stag, its legs locked straight, its head jerked upward, its eyes bulged, and its mouth opened in a long, agonized cry.
The sound rang several times through the night sky, startling birds from the trees.
Its skin began to writhe, as though something were moving beneath the fur. It was Voldemort's face, forcing its way out through the back of the stag's neck, those snake-like eyes preparing to open.
And then—
Bang.
Gunpowder and metal in chorus.
A bullet tore through the stag's skull.
The body froze in mid-motion for one instant, then collapsed, utterly freed at last. It probably passed on far more peacefully than it ever could have under the Dark Lord's claws.
"?????"
Voldemort's face had barely emerged halfway from beneath the stag's skin before the host was gone. His eyes had not fully opened. His mouth had not fully formed.
His nose... well, Voldemort never had much of one to begin with.
Before he could even process what had happened, he heard a voice he would never forget.
"Quick! Quick! Magic Skeleton, come take a picture! I just put down a huge stag. This thing could feed me for a month! And afterward you can use the bones to build yourself a pair of wings!"
With the sound of footsteps, Voldemort saw that familiar little wizard running over.
The boy wore cartoon-print pajamas. His hair looked like a bird's nest.
Most importantly, he was still holding a long gun with smoke trailing from the barrel.
"?????"
Voldemort no longer had the luxury of cursing or ranting at the murderer of his deer host.
The moment he saw the little wizard Dumbledore had cultivated, he went straight into fight-or-flight.
"Why is it him?!"
Dumbledore had once stripped him of the ability to love.
And now, with this new "work," Voldemort strongly suspected Dumbledore had simply removed the ability to have a normal brain at all.
"Damn that deranged Dumbledore! He wants the new creation to personally destroy the old one, just to prove the new version is better!"
At a moment like this, running was the only option.
Voldemort's instincts were excellent.
His reflexes, unfortunately, were not.
His remnant soul tried to flee on instinct.
But before he could move, the little wizard approaching the stag suddenly leapt.
"What's this? A bonus drop!"
His body spread in midair like a pouncing cat. Both hands shot forward, ten fingers wide, and in one grab he caught the pale mist.
"My God! Is this a sprite? No—wait, maybe it's a spirit ring!" Iain landed, both hands cupping the struggling remnant soul, eyes shining like stars.
"I actually got a spirit drop at Hogwarts! Magic Skeleton, it turns out this whole world is just one giant fantasy crossover!"
"No wonder it's a fairy-tale world. It doesn't care about copyright at all. I love it!"
Iain's voice was full of pure delight.
Voldemort's remnant soul writhed in his palms like trapped fog, like a snake pinned right behind the head. He wanted to curse. He wanted to roar.
But before the first insult could even form, he felt the little wizard force something open and start stuffing him inside.
"Oh, thank you, generous universe, for this lovely wand spirit."
It was Iain's wand.
And also Iain's very first dream.One small line tweak for your earlier sentence: "After one night of wandering through that strange underground palace in his dreams, his body needed real rest before it could recover."