Bosses always had access to more attacks and spells than a player of the same level. However, they were still subjected to a limitation of spell slots. Therefore, each time a party entered a dungeon, a spell list for bosses were created. For some bosses, their spells were randomly selected from a pool of learned spells, but for others, the selection could be influenced by a number of hidden flags.
At this point, Manco had figured out the group's purpose wasn't to kill the boss, but to learn a spell from it. They seemed to possess a Beta Gear that allowed the owner to learn spells from a boss, and had been trying to set up the conditions to do it.

This explained the group's earlier actions, such as heading toward two dead-ends, entering the boss room using the ground-level entrance, and dragging out the fight before surrounding the boss and attacking it at range. They had been trying to get the boss to use that spell which looked like acid spray. The witch would try to copy that skill. If they die and anything drop, she would be the one to pick it up.

Ideally, she would be the last survivor, and use the invisibility cloak (which he suspected was another Beta Gear) to evade the boss' attention. Eventually the boss would shift from 'Aggressive' mode to 'Idle' mode. At that point, the boss room would be unlocked, allowing her to sneak out of the dungeon.

That would work quite well in theory. And in practice, too. Until Manco came along. He had left his hiding place and was crouching on the suspended balcony, which was previously occupied by skeleton archers.

Holding the skull wand, he maintained the Marshland spell and saw something slowly sinking into the affected area, which had turned to a mini-quagmire. He had spotted Morana the moment she disappeared and knew exactly where she was. Then it was just the matter of using to the spell to trap her.

To her credit, she still managed to hold still even as she was waist-deep into the ground.
Then again, the lich was in combat mode, and was roaming around the area trying to look for the intruder. If she showed herself, the boss would be upon her in seconds.

After a few more seconds, he deactivated the spell, and the ground began to harden. It would take considerable strength to break out, which he doubted a witch would be capable of.

'I almost feel bad about this,' Manco thought as he loaded his crossbow with a Broadhead bolt.
Poking his head just enough for a clear shot, he fired at what he guessed was her center of mass.
[Power Shot]!

The bolt zipped through the air and hit the invisible midair. Immediately, an agonized cry sounded and the cloak's camouflaging effect worn off.

"There you are!" A triumphant hiss let him know that the boss had noticed the hidden intruder. Manco lied flat on the balcony and held still while he closed in on his target.

"Who was that? Who the fuck was that?" An angry voice drifted up from below.

The question was punctuated by a fireball zipping over the balcony railing and hit the wall in front of Manco, showering him with fragments of stone and cinder. Morana must have figured out his location based on the crossbow bolt's orientation. He ignored her and stayed silent.

"Show yourself! You sneaking piece of shit!" The witch followed her demand with a string of colorful expletives, only stopping to scream in pain as the lich unleashed his spells on her.

Manco listened to the sound of attacks and curses below. Within a minute, it was over.

'Hmm. I wonder if she's learned that spell,' he idly thought.

After several more minutes of patrolling, the lich went back to the throne. The sound of its wheezy breathing got softer as it got further away. Then Manco heard a loud scraping sound as the massive door opened, letting him know the boss was back to idle mode.

Peering down from the balcony, he saw something sparkling where Morana had fallen. Slowly, he made his way down to the entrance and scooped up the item, then left the boss room to inspect it.

"A monocle?" He held up the item, which was a golden loop of metal wrapping around a transparent glass lens.

〘Mimicking Master's Monocle〙(Unique)
- Type: Accessory - Eye wear
- Effect: Awareness +8%
- Active Effect: Mimic
+ Learn any spell or technique.
+ The learner stands within 25 meters of the teacher and watches the execution from start to finish a few times.
+ Base chance to learn: 80%. Base numbers of watches required: 2. Actual numbers vary based on the two parties' levels, attributes, spell complexity and other factors.
+ The spell or technique is condensed into a memory crystal.
+ Can create a maximum of 5 crystals. After that the item becomes unusable. Uses left: 3/5
- Notes:
+ 40% chance to drop upon owner's death.
+ Only works on hostile NPCs
—.—

 "Nice!" He commented. "Too bad she only dropped one item!"

Some of the most powerful and destructive spells in the entire game were possessed by bosses. These could not be learned anywhere except by using items like this one. However, learning them was quite difficult, considering one had to stand quite close to the boss, which was already risky enough. In addition, many spells could vaporize players within seconds, long before they could learn anything. Even a simple lich required several people to act as guinea pigs so that one person can learn the boss' spell.

'But why that spell, though?' Manco scratched his head. Albeit powerful, that acid spray variant would be outclassed after the playerbase got pass level 50…

'Ah, of course. The tournament.' He nodded. He almost forgot. At that point, most players would be around level 50, so very few would possess a high tier cleansing spell. This would mean easy victories for her if she used this spell at the right moment. Besides, she had already learned two spells using this monocle. It looked like she was trying to use this thing up as quickly as possible to avoid losing it. Which was an entirely valid concern, considering what just happened.

Looking back into the boss room, he saw the lich slowly regenerating his health.

He did some mental calculations. By now, the witch should have already respawned and regrouped with her party. Then what would they do?

They might rush to this dungeon as fast as they could. Of course, they wouldn't be able to enter this specific instance again, but they might camp outside to catch him exiting it. Earlier they had spent one and a half hour  to get here. Even if they rush, they wouldn't be able to move much faster than before.

Or, they might also be waiting in the town for him to return.

Whichever option they picked, he had at least an hour to kill the boss and loot this place.

"Alright, my turn!" Manco equipped the monocle. Having seen the boss' arsenal of spells, he had picked the one he needed the most right now.

After adjusting his loadout to better fight the undead, including exchanging the vials of poison for holy water, Manco climbed up the balcony and slowly made it toward the throne at the far side of the room.

The Lich Count was sitting on his skull throne, looking tired. Its health bar was at about 15% and slowly creeping up. Apparently it had no healing spells and had to rely on its underling to heal it. In just a few moments, it would gather enough mana to resurrect those creatures.

Taking out a vial of Alchemical Fire from his belt, he gave it a shake. Then he stood up and looked down at the boss.

「Mimic」!

At the same time, he threw the vial. It sailed in a parabolic arc and shattered right between the lich's bony feet, spreading orange-green flame that clung to the throne and his robe.

Emitting a painful howl, the lich disappeared in a puff of smoke. It had teleported away from the throne.
〔Success!〕〔Mimicry progress: 0% -> 51.5%!〕

Ignoring the message, he scanned the room to search for the boss.

A putrid smelling gust of wind blew at him from behind.

"Shit!"

Without thinking, he dove headfirst over the balcony railing. Behind him, he heard the hiss of corrosive eating through wood and stone.

-35!

He landed on his back and rolled to his feet. The fall took away some health but did not dislocate anything.

Turning back toward the boss, who was now up on the balcony, he fired his tier-0 spells while slowly retreating.

「Mana Bolt」!
「Fire Bolt」!
「Shadow Bolt」!

One projectiles after another shredded the balcony railing. Howling in pain, the boss ducked to avoid his attacks.

"Hey, come down here!" Unable to get a clear shot, he chucked a Fireball at its approximate location.
The gob of fire burst right above the boss, briefly setting it on fire and prompting another angry hiss.

"Alright, suit yourself!" Manco jumped up a pillar fragment to have a better line of fire to the lich and fired a Mana Blast.

The projectile hit it squarely in the head and exploded. With an angry howl, the lich jumped down from the balcony. Glaring at Manco with its fiery eyes, it charged straight at him.

"That's more like it!" He said, unsheathing his daggers, which had been doused in holy water.
Seconds before collision, he crouched and dodged to the left, avoiding its powerful swipe. Pressing down on his heels, he bounced back up and drove the dagger into its torso.

「Armor-Piercing Stab」!
-73!
-15!
-14!
...
As the holy water steadily attacked the undead body, Manco unleashed his familiar combo.
The initial strike temporarily lowered the enemy's damage resistance. Next came Flurry. Chunks of putrid flesh flew away from the undead body.

The lich howled and defended itself with its arm and occasionally striking back ineffectually.
All the while, Manco paid close attention to its burning red eyes. Specifically, he waited for them to glow green.

'There!' He dodged to his right, just in time to avoid the spray of corrosive liquid.

「Empowered Strike」!
-156!
-16!
-17!
-16!
...

The upward blow struck the lich's neck, nearly severing it. The undead staggered back, holding its head back in place.

Sheathing one of his daggers, Manco retrieved the second vial of Alchemical Fire and prepared to throw it.

Having learned the effect of the vial, the boss immediately teleported away. Which was exactly what he had hoped for.

「Mimic」!
〔Success!〕
〔Mimicry progress: 51.5% -> 100%!〕
〔Spell learned: Spatial Displacement I〕

"Alright!" Manco grinned. The percentage learned depended heavily on the type and tier of the spell in question. Higher tier required more attempts, that much was clear. However, offense oriented spells also took longer to learn. Low-tier utility spells could be learned in two or three tries.

He took out his gun. Time to finish this fight.