The sound was initially faint, but soon grew louder. Olivia turned her head to look down the dark staircase and saw something terrifying. She let out a scream and ran towards Harry.

Upon hearing Olivia's scream, Harry turned around and saw the staircase leading to the rooftop. A black Water Rat Beast darted out of the darkness, followed by more and more of its kind.

These Water Rat Beasts had previously floated on the surface of the water. Instead of climbing the walls, they had all crawled into the 30th floor of the building through a window. Now they appeared on the rooftop, climbing up the stairs.

Olivia panicked at the sight of the group of Water Rat Beasts and ran towards Harry.

Harry knew it was not good. Olivia was no match for these Water Rat Beasts. If one of them pounced on her, she would be in danger.

Just as he had dodged the attack of the Leviathan Lizard in front of him, Harry jumped to the side of the lizard.

The Leviathan Lizard lowered its body slightly, and Harry immediately understood that it was going to whip its tail.

As expected, the Leviathan Lizard slammed its tail down heavily behind it.

Having anticipated the move, Harry had gripped his iron rod tightly and swung it diagonally towards the ground. The veins on the back of his hand bulged.

The Leviathan Lizard's tail slammed heavily onto the diagonal iron rod.

With a loud "bang," the iron rod trembled and Harry felt his right arm go numb.

The Leviathan Lizard's tail was incredibly powerful, but not strong enough to bend the iron rod with one hit. Instead, it was bounced back heavily, allowing Harry to close in. He clenched his left fist and launched the "Fangs of Gluttony," which pierced into the Leviathan Lizard's head. He then used the momentum to grab its head and carve out four deep blood grooves.

All four Fangs of Gluttony plunged in, slicing downwards, causing fatal wounds. The four blood grooves were filled with copious amounts of blood rushing out.

New information came to mind, and he obtained two more Spiritual Sources. His stash was now at Spiritual Source 13/20.

Harry succeeded, and on the other side, Jackson was not far behind. He successfully approached the Leviathan Lizard and struck it on the forehead with his right hand, activating "Soul Devourer."

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However, he was a level 3 Spiritweaver, and killing a level 3 Leviathan Lizard would only yield one Spiritual Source, unlike Harry who could obtain two. Currently, he was only five Spiritual Sources away from promotion, while Harry was still seven short.

Olivia rushed to Harry's side, looking frightened. Five or six Water Rat Beasts appeared at the stairway, fanning out and attacking Olivia, Harry, and Jackson.

After defeating the Leviathan Lizard, Harry felt a surge of energy from the Spiritual Source he obtained, and was about to charge towards the Water Rat Beasts. Suddenly, the creatures stopped in their tracks and turned around, rushing back towards the darkness at the stairway.

"What's going on?" Jackson asked, brandishing his shovel and about to attack the Water Rat Beasts before realizing they were running away. He then burst into laughter, "Did we scare them off?"

Harry's heart skipped a beat as he noticed that they could not have scared off the Water Rat Beasts. The only possibility was...

When Harry turned around, he saw three heads appear at the edge of the rooftop, the lizard heads of the Leviathan Lizard. Three huge Leviathan Lizards then climbed up onto the rooftop.

"Perfect timing!" Jackson grinned, not afraid of these Leviathan Lizards despite their poison. Having recently slain a few of them, Jackson had gained some experience. He was only five Spiritual Sources away from promotion and needed to hunt more monsters to obtain them.

As Jackson spoke, a huge black shadow emerged from behind the three Leviathan Lizards, and a large monster the size of a table jumped onto the roof.

It was a giant crab, with a grey body and a shell over 1.5 meters in diameter. Its two crab claws were massive, almost 2 meters in length. It pounced on one of the Leviathan Lizards, and with a single claw, it cut the creature in half, causing Harry and Jackson to gasp in shock.

They had tried to attack the Leviathan Lizard with iron rods and shovels, but despite their efforts, they had not been able to inflict much damage. The creature's toughness was evident. But now, it had been cut in half by the giant crab's claw. How sharp and powerful must that claw be?

As the three were stunned, the giant crab swung its claws at the Leviathan Lizards again. One was hit and flew off the roof, while the other had its tail caught in the crab's claws, struggling to break free before eventually falling off the roof and disappearing.

The giant crab was not interested in the Leviathan Lizards, but in Harry and his companions. The attack on the Leviathan Lizards was just to clear the obstacles in its path. It quickly moved towards the three of them.

"Retreat!" Harry yelled, realizing that they were no match for the monster. If they fought, there would likely be casualties. He grabbed Olivia's arm and rushed towards the stairway, with Jackson following close behind, shouting, "I get it now, the rats were scared off by it, not us!"

Harry thought to himself, "You're only realizing that now?" He pulled Olivia along and rushed into the stairway. Jackson stood at the entrance, wielding his shovel and preparing to attack the giant crab, which had just hit the entrance with a loud crash.

"Phew, that was close. It's too big to come in here," Jackson breathed a sigh of relief and then stood guard at the entrance, ready to attack the giant crab if it tried to enter.