Ivan was impressed by Sirius's quick wit in dispelling the Inferius with only an enhanced version of the Illuminating Charm.
It was extremely difficult to deal with hundreds of Inferi underwater, and Ivan estimated that he would have to transform into a basilisk to do so, but he did not have that much magic at the moment.
However, the Illuminating Charm was the only cure, and the banished Inferi could return at any time.
Coupled with the greatly reduced range of the Luminous Spell in the black lake, it took more magic than usual to dispel these Inferi, so it did not take long.
Knowing full well that he was not out of danger yet, Sirius pulled Regulus, who had been petrified, to his feet and swam on, pulling Ivan with him.
Ivan also dragged Kreacher, who was still a little dizzy from being stuffed full of lake water, after them.
They were now quite a distance from the island, so neither of them swam back towards it, but instead travelled as far as they could, hoping to reach the shore.
However, there were too many Inferi along the way, so Sirius and Ivan had to alternately cast the Illuminating Charm to disperse the approaching Inferi.
The cold water of the lake was sapping their strength, and Ivan had no idea how long he had been swimming. He had little magic left, and his body was growing numb.
Ivan stares into the darkness, wondering if Sirius is lost and they might drown in the lake today.
Fortunately, Sirius proved to have a good sense of direction, and a few moments later, Ivan was able to see the bottom of the lake and the rocky shore of the lake in front of him.
Sirius, who was swimming in front of them, cast another Improved Illumination Charm and swam all the way to the shore, where he grabbed hold of a rock groove and climbed up it.
"Quick, give me your hand!" Sirius called out as he helped Regulus and Kreacher settle down, then hurried to Ivan and pulled him up with him.
Suddenly, a wet, pale hand reached out from the lake and grabbed Ivan's thigh, trying to drag him down.
Yvonne looked down and saw the dead woman who had grabbed her. Her mouth was wide open, her face ferocious, her eyes wild.
"Sectumsempra!" Ivan did not hesitate to wave his wand.
The invisible blade of magic sliced through her gaping mouth, slicing off half of her body. Her severed limbs and organs fell straight to the lake, but strangely, not a drop of blood flowed out.
Unencumbered by the Inferius, Sirius managed to pull Ivan to shore, and as he stared at Ivan's ashen face, Sirius asked worriedly, "Are you all right, Ivan?"
"I'm fine, but I think we need to hurry!" Ivan said, shaking his head. He turned to look at the Black Lake, where more Inferi were climbing out of the shallow mist.
"Kreacher, can you teleport all three of us at once?" Sirius asked.
Kreacher hesitated for a moment, then gritted his teeth and said that he could only teleport two people at once!
Ivan and Sirius were both disappointed, as Kreacher alone would not have been enough unless they were willing to give up Regulus.
This was because Kreacher had made it clear that it could not sense the interior of the cave, meaning there was no second chance of teleportation.
Unless they were willing to swim through the crack in the rock again, as they had come, they would not be able to do so.
"We'll have to find Professor Lupin and Dobby soon!" Ivan said. Two house-elves should be able to teleport all four of them away.
Although they were now ashore, they were not in the same location as when they first boarded the ship. Instead, they were on one side of this vast black lake, and the mist that was spreading around them was also blocking their connection.
"We'll just make as much noise as possible and let Lupin know we're on shore!" Sirius quickly came up with a solution, waving his wand at the approaching Inferi.
"Inndio! (fire roaring)"
A streak of fire shot out from the tip of the Sirius wand and struck one of the Inferi, but it only managed to ignite a small flame before it extinguished itself.
"Have you used up all your magic, Sirius?" Ivan asked, unable to contain his laughter.
'No, I just used a lot of magic to do it!' Sirius's expression was serious, not at all joking.
Ivan's smile faltered, and he tried to cast a Fire Charm. The spell, which would have created a sea of fire, was now just a faint flame.
He immediately realised that Voldemort had placed restrictions on the Fire Charm!
Just as Harry could not create water out of thin air in the middle of the island, fire magic was presumably restricted and weakened.
If even they knew that Inferi were afraid of fire and light, how could Voldemort have overlooked it?
The Luminous Spell could be cast freely and could also be explained by the need for illumination in the pitch-black cave, but it would be unreasonable not to limit the use of the Fire Charm, a powerful weapon against Inferi.
No matter how much Voldemort divided his soul, he would not be so stupid…
In the original timeline, Dumbledore was able to cast this spell most likely because of his skill with magic and his possession of the Elder Wand.
"Dropped to pieces! Stupefied!" Sirius struck down a large number of Inferi with his magic.
Ivan, on the other hand, released an extremely powerful beam of light in an attempt to force the Inferi back and signal to Lupin where he was.
However, the situation did not improve. Countless Inferi were climbing up the rocks from the black lake in an endless stream. They staggered towards them and stared at them with their empty eyes filled with desire and madness.
Ivan didn't think their magic could deal with such a large group of Inferi.
He tried to think of a way out of the situation, suddenly realising that he might have a chance at an enchantment that would allow him to break through.
However, there was only one such opportunity, and it was not worth it to cast the Fire Charm on it.
Ivan couldn't help but think of the Fire-Risking Charm he had once read in The Secrets to a Cutting-Edge Dark Magic!
The kind of dark magic that uses everything it can burn as fuel to achieve self-expanding growth!