Saving Vesper had turned out to be a fruitful endeavor.

  [Evolution to Vampiric Bat (D) is complete. As a reward for reaching D grade in your Vampiric Bat form, you have been rewarded a suitable new skill and passive.]

  Skill Unlocked:

  [Piercing Fang (D)] Lunge at a target and bite with mana-hardened fangs, dealing heavy damage and applying a bleeding debuff. If used from stealth or in darkness, the attack is a guaranteed critical hit.

  Passive Gained: [Nocturnal Vitality]

  While in darkness or shadow, you regenerate stamina and mana 25% faster. Also grants minor lifesteal on melee attacks during nighttime or in low-light environments.

  Since his Vampiric Bat form reached level 10 during the battle to save Vesper, he evolved it after reuniting with the humans and wiping out some more stray bats on the way. Just like with his Undead Mage form, it didn't upgrade into a higher species, but he was rewarded with a new skill and a passive.

  Speaking of evolutions, killing the stray bats on the way back had netted him a very exciting system notification.

  [Necroplague Slime] has reached Level 50 (B Grade). Evolution is available.

  Do you wish to begin the evolution process?

  [Yes/No]

  "Randy, Vesper, Valoria, I've reached level 50 and need to begin my evolution," he said to the humans after opening his beady eyes from having just finished his Vampiric Bat evolution. "Can you three protect me for around an hour?"

  "Level fifty?!" Valoria blurted out in shock. "Since when did you get so strong?"

  "Recently?" Xen replied, understanding her shock. Even for him, this had come out of nowhere. "It would seem that leveling up comes quite fast when I'm wiping out hordes of monsters by myself."

  "I knew solo leveling was faster than working in a team, but I never would have thought it could be this ridiculous," Randy said, shaking his head in disbelief. "But don't worry, we will protect you with our lives while you evolve. Right, guys?"

  Both Vesper and Valoria nodded with determination.

  Xen hoped they would, considering he had saved them all multiple times by now. While he still wasn't a hundred percent comfortable leaving his life in their hands, especially considering just how weak they were right now, he didn't have another choice. He was only given an hour to start the evolution, and it would take longer than that to reach the fifth floor and the teleportation hub to the surface. If he had to evolve, he would rather do it here, where he had cleared out most of the monsters, than on a brand new floor with stronger enemies lurking.

  "Thank you," he said, walking over to a small alcove in the cliff face and folding his enormous wings to fit inside. "Orbs of Light," he incanted, flooding the area with light. "These should grant a level of protection while I'm sleeping."

  "Just leave it to us," Randy said, giving him a thumbs up as the three humans formed a defensive line just outside the alcove's entrance, with the orbs of light hanging over them.

  Xen nodded in appreciation and told his system to begin the process.

  [Generating evolution options...]

  [Having already selected your primary evolution path, fewer evolution branches are available moving forward. However, due to your extensive list of achievements, two evolution options are available to you.]

  "The same system message as last time," Xen mused as the message vanished and was replaced with the two new options.

  Select your path forward. Warning: Evolution choice is permanent.

  [Option 1: Plague Sovereign Slime]

  An advanced evolution of the Necroplague Slime that embodies the concept of a living epidemic. This form excels at area denial, contagion, and corruption-based battlefield control. The Plague Sovereign is feared by Hunters and monsters alike for its ability to turn entire battlefields into zones of decay that it alone rules.

  Unauthorized tale usage: if you spot this story on Amazon, report the violation.

  Skill: [Virulent Bloom (B)]

  Infect a target area with a seed of corruption that blooms explosively after 3 seconds. All enemies caught in the bloom's radius suffer stacking necrotic damage over time and have a chance to spread the infection if they move or touch another afflicted being.

  Passive: [Contagion Lord]

  Debuffs applied by your corruption or plague-based skills now have a chance to spread to nearby enemies each tick. Spreading effects apply at 50% potency but with a refreshed duration.

  Xen read over the first option and had mixed opinions. The name called out to him. He liked the idea of being called a sovereign, and this evolution was supposedly the upgrade to his current Necroplague form. As for the evolution's capabilities, it seemed to work best when fighting alone. The idea of facing off against a horde of monsters, unleashing plagues buffed by his Solo Hunter passive, sounded impossible to fight against.

  But he didn't miss the key part that mentioned: The Plague Sovereign is feared by Hunters and monsters alike for its ability to turn entire battlefields into zones of decay that it alone rules.

  Since he planned to integrate into human society and would likely work alongside others in the future, turning battlefields into swamps of decay would force him to work solo.

  "Though I could always simply refrain from using the full potential of the Plague Sovereign form and rely on the skills from my other forms," Xen reasoned with himself. It's not like he had to unleash plagues when others were around. "This one certainly has some potential. Let's see what the other option has in store for me."

  [Option 2: Hexreaver Slime]

  Where the Necroplague focused on curses and disease, the Hexreaver is a precision blight caster, capable of layering debilitating hexes and shattering enemy defenses. It specializes in curse weaving, burst corruption, and anti-boss capabilities.

  Skill: [Perish (B)]

  Target an enemy afflicted with 3+ debuffs. All active debuffs are violently amplified, dealing a burst of damage based on their cumulative strength. If the target dies while under this skill, nearby enemies receive a fear effect.

  Passive: [Hex Catalyst] For every unique debuff on a target, your damage against them increases by 20%.

  Xen's focus instantly locked onto the new passive that would provide a twenty percent increase in damage for every unique debuff he could inflict. If he had learned one thing from possessing the Solo Hunter passive, it was that percentage-increasing passives were utterly broken.

  He could also see why the system said the Hexreaver Slime had anti-boss capabilities. The only way to solo a boss was to either drag it to your level with debuffs or raise your own strength with buffs to try and match it. This new evolution provided both a skill that amplified debuffs and a passive that increased his strength.

  "I think it's obvious which is better for me," Xen chuckled. As much as he saw the appeal of Plague Sovereign, he didn't need any more help with wiping out hordes of small fry. What he needed was the ability to kill enemies far above his level, and that's what Hexreaver Slime would allow him to do.

  The funny part was that if not for his Shapeshifter class providing him with so many different skills from other forms and human classes, the Plague Sovereign slime would be the better choice, as he doubted people feared wild Hexreaver slimes nearly as much as Plague Sovereign slimes.

  "System, I pick Hexreaver."

  [Evolution to Hexreaver Slime Confirmed: Time until completion 119 minutes and 58 seconds]

  Darkness clouded his vision, and he slowly fell asleep.

  Just in time to hear the screech of an incoming bat.

  ***

  [Evolution to Hexreaver Slime (Rare Variant) is complete]

  [Pending experience can now be distributed]

  [Hexreaver Slime] has leveled up: 50 -> 51.

  [Vampiric Bat] has leveled up: 10 -> 12.

  Xen jolted awake. Dismissing the system messages, he rushed out of the alcove into the darkness—seeing the three humans still alive, he sighed with relief. His Orbs of Light had long faded, and there were signs of battle from the odd bat corpse lying on the pathway.

  "Well, look who's finally awake," Randy said, wiping the sweat from his forehead. "I thought you said it was going to be an hour?"

  "Evolution took longer than expected," Xen admitted, glancing around. "How did you handle the bats?"

  "I shot them down with mana arrows mostly," Randy said. "I even leveled up to twenty-eight."

  "Good job," Xen said, calming down. The humans were safe, he was alive, and his evolution had been a success. "Let's get a move on—ah, wait, let me switch forms to carry Vesper."

  [Do you wish to take on the Hellfang form?]

  "Yes," Xen agreed, and his Vampiric Bat body dissolved into sludge. His black slime body, which looked glossy now like hardened marble, was briefly exposed as the body of a massive Hellfang reformed around him, crafted from his biomass reserves.

  "Terrifying," Randy admitted, stepping back and holding his nose from the stench Xen let off during his transformation. After a few minutes, he had transformed into an eight-foot-long wolf that would make the wolves on the first floor look like puppies. He flexed his toned muscles, barely hidden below his molten-colored fur.

  Then he stood up.

  Unlike the wolf that had strictly run on four limbs, the Hellfang could walk upright like the Demonic Gnoll he had killed to acquire this form. While towering over the three humans, he flexed his dagger-sized claws and grinned in satisfaction. Even at such a low level, he could tell not all forms were made equally.

  The Hellfang was dangerously strong.

  He set himself back down on all fours and glanced at Vesper. "Get on, we are going to head to the entrance to the fifth floor."

  The humans worked together to haul the hurt assassin onto his back, and once he was secured, they headed forward.

  For the fifth floor.