Lizardmen War was a conflict between the Great Tomb of Nazarick and the Lizardmen Alliance. Initially orchestrated by Nazarick to massacre the Lizardmen and turn them into Undead, they later decided to conquer them instead.
To strengthen Nazarick's military force, Albedo had suggested using the corpses of the newly located Lizardmen, as there is a better chance they might create more powerful undead than using human corpses, who are fairly weak. In that end, Nazarick turned its attention to the Great Lake. An undead emissary was sent to each of the five tribes of Lizardmen: Green Claw, Red Eye, Dragon Tusk, Small Fang, and Razor Tail. The undead gave the Lizardmen an ultimatum from its master the Supreme One of their impending destruction. It was declared that in eight days' time they all would perish before vanishing.
Though the Lizardmen's morale initially to plummet due to the overwhelming power of the appearance of the undead, one of the Lizardmen from Green Claw, Zaryusu Shasha a Traveler, proposed that the tribes unite together in order to survive. Green Claw having already made allies with Small Fang and Razor Tail in a previous conflict, commissioned Zaryusu to entreat the other remaining tribes into the alliance. Zaryusu having reached Red Eye, fell in love with its chieftain Crusch Lulu, who agreed to the unity of the tribes. Dragon Trusk was also brought into the fold after the Traveler earned Zenberu Gugu's respect through a duel.
All the tribes gathered at Green Claw for a meeting to mount a plan of defense and attack for the coming war with the Supreme One. The tribes then began to make preparations such as building fortifications for themselves and training for the battle.
At the appointed time, the Army of Death emerged from [Gate] with 4,950 strong undead. In comparison to the Lizardmen Alliance who numbered 1,380 people, the battle had the odds of three-to-one. Cocytus who was designated as the General of the undead army.
However, he was given specific rules from Ainz Ooal Gown. The first rule was Cocytus was forbidden from setting foot on the battlefield. The second rule was his elder lich he was given to command the undead was to be used until the end. The third rule he was to think independently on this campaign. Cocytus keeping these directives in mind directed his orders via Message Scrolls and gave the order for his forces to march on the attack.
Upon seeing the approaching army, the tribes enacted a ritual ceremony uniting the tribes in great fanfare forming the Lizardmen Alliance. The lizardmen and undead armies advanced upon each other through the wetlands. The zombies and skeletons that were the first to advance drew apart due to their varying physical constraints. The first engagement thus was with the skeletons and lizardmen who employed no formations but simply crashed into the undead. Led by the five Head Warriors, who were backed up by 89 armored warriors from Razor Tail, they charged at the skeleton horde as a single united wall. The lizardman squadron tore into the skeleton horde, having an incontestable advantage in the first engagement. The skeletons being made of bones were easily crushed by the lizardmen with their weapons and protected from the undead's rusty weapons by their tough scales.
While some lizardmen were hurt, nobody sustains fatal wounds. From the first charge, 500 skeletons lay in fragments. Cocytus watching from his station was astonished by the display as the demi-humans had exceeded his expectations. Understanding that the skeletons and zombies would probably only serve to sap the oppositions' stamina, the outcome of the battle would still be in favor of the lizardmen. Having only an effective troops of 300 Undead Beasts, 150 Skeleton Archers, and 500 Skeleton Riders the weight of numbers were now against his army. Seeing that the state affairs were not good the Floor Guardian made a decision to draw out the battle to wear the lizardmen down. Using a Message Scroll, he sends out a command to the army's commander.
On the other side of the battlefield, the chieftains begin to look at the undead's battle strategy with suspicion. The reason is that the undead are not mobilizing effectively against them. Some inquire perhaps the enemy is looking down on them, but this proves to be the lizardmen's advantage as they are winning. They suspect that the undead army has no commander to give orders, instead of relying only on numbers to obtain victory. Still, preparations were going well on their side by their druids led by Crusch Lulu and were confident that their unity would prevail.
The skeleton riders then began to move en masse. Seeing that the mobility of these undead would be a problem, the chieftains decided to respond accordingly. Just as the riders were circling the Lizardmen on the battlefield they fell into traps laid out by the Lizardmen Alliance. Exposed and on the ground, from their mounts, the skeletons were eliminated one by one using throwing stones.
The battle situation had then begun to change, the skeleton archers launched volleys of arrows at the melee. Not expecting the hail of arrows, many lizardmen were hit forcing themselves to divide between blocking the projectiles and fighting the undead. The skeletons were immune to piercing damage were not hurt. It was a near-perfect strategy, but the undead had used it too late and the lizardmen rushed through the firing area, ignoring the passing skeletons to target the archers. Thanks to their thick skin and scales, the lizardmen were able to go through with minimal casualties. The archers without any orders to adjust to this tactic only kept firing at the enemy until they were drowned by the rising lizardmen tide.
At this point, the only undead left on the battlefield still active were the zombies, with most of the skeletons beaten to the ground. Cocytus's command eventually reached the zombie beasts that began to flood the battlefield in a huge uncoordinated formation. The attack from below was unexpected by the lizardmen who now had to contend to undead tearing at their legs. The increasingly fatigued demi-humans were now pressed against defending themselves from these attacks.
Those too slow were mauled to death by the beast zombies. The Head Warriors who had led the lizardmen on the front lines were now being pressed back. Just as they believed the line of battle would break, the ground before them swell, revealing two Swamp Elementals summoned by the druids. Acting as their trump cards, the summons charged into the zombie beasts and attacked them with their tentacles. Both entities knew no pain, but the battle went in favor to the elementals on strength rekindling the lizardmen's courage for another charge. A battle ensued but victory was at hand for the lizardmen who had the advantage of numbers.
From afar, Cocytus saw that Nazarick would lose this battle if he did not act. Realizing that the reason for his forces downfall was the lack of intelligent undead in it ranks. He still had a way to turn the tables from this, but before he implemented it he used a [Message] scroll to contact Demiurge for his insight. Cocytus asked for his advice to avoid a disgrace.
The demon provide that perhaps failure was the intended purpose that Ainz deemed, as why would the Overlord give Cocytus command of such an inferior force and restrictions barring him from participating. Demiurge went on to say it was probably to give Cocytus to improve how he approached such matters. After ending the message, Cocytus pondered on how to proceed, though he hastened to act after seeing Entoma Vasilissa Zeta, an observer for this confrontation, using a talisman to communicate to Ainz. He ordered the Elder Lich Commander, Iguva=41 to enter the battlefield.
The undead magic caster upon receiving its order commanded two Blood Meat Hulks to kill the attacking lizardmen. The monster obeyed and began to kill any warrior they came across. The two bought the lich enough time to advance across the field unhindered. Now alone, he complied with his orders to show the lizardmen his power.
The lizardmen warrior having eliminated all the beast zombies, were fatigued by the battle were called by the Head Warriors to move out to allow the injured back to the village. Though they were distracted by the searing heat that engulfed the area and the swamp elementals which were destroyed. The onrushing lizardmen were incinerated by a ball of flame by the elder lich. The disparity between the warriors and the magic caster was apparent. To ensure a message went to the chieftains, the Head Warriors ordered all the survivors to escape whilst they confront the lich to buy time.
News of the new undead commander only a hundred meters away was brought to the chieftains. The undead had began to close the distance and began to execute are-of-effect attacks. Zaryusu, Zenberu, Crush, and Rororo take to the field to combat Iguva=41. Iguva=41 walked ever closer to the village, planning to continuously launch [Fireballs] to destroy the demi-humans. He spotted the hydra, Rororo, coming at him. Thinking it was their ace in the hole, Igyva=41 believed that killing it would cause the lizardmen to lose the will to fight. Conjuring [Fireball], he struck the hydra dead center.
However, the hydra pressed on and continued forward. Rororo continued running even though it was wreathed in flames as it was enchanted by defensive spells to reduce damage. The lich frustrated by the pest continued its fireball attacks at the persisted beast. Though just as the lich began to fire a killing blow, Zaruysu who had been hiding behind the hydra used the Frost Pain activate an [Icy Burst] blocking the attack.
It was evident that Rororo had acted as a shield to allow the three lizardmen to cross the distance to reach the magic caster. The lich saw that his fire-based attacks were being countered by the lizardmen wielding Frost Pain. Being at an disadvantaged now that the lizardmen were nearly 40 meters closer to him, he casted [Lightning] but the shock was absorbed by Zenberu who used monk ability [Massive Resistance] to reduce the magical damage. It allowed the Traveler to get closer to the undead at 20 meters. Realizing that he was up against powerful enemies, Iguva=41 summoned four Skeleton Warriors to protect him.
The Traveler was only 10 meters away and closing from the lich. Iguva=41 attempted to maintain his confidence offering them to surrender if they bow before him, and he would allow them a quick death. The lizardmen refused his offer, with Zaryusu raising Frost Pain against the magic caster. Zenberu charged at the skeleton squad, smashing them with his fists, though the two skeletons held off his onslaught. It allowed Zaryusu two less warriors to deal with as he passed them. The remaining warriors attempted to strike him, but were hindered by Crusch who used [Earth Bind] to entangle the undead. Zaryusu r=the rushed at Iguva=41 who casted [Scare] to intimidate him, causing the lizardman's resolve to wane, but it was countered by Crusch's [Lion's Heart] spell.
Greatly annoyed by the interference, the lich attacked the druid with [Lightning]. Zaryusu though hearing his companion's pain did not look back, intent on killing the lich with the opening Crusch had given him. The lich turned to late to counter, allowing the warrior to knock Iguva=41's spell casting finger. The lich was vulnerable at close range, however Zaryusu Iguva=41 and suspected his slash attack faced resistance to a skill of the undead.
Three arrows of light appeared before the lich and shot at Zaryusu, who attempted to parry the bolts with his sword. The magic arrows went through the blade, and pierced his body causing pain to erupt in his body. The [Magic Arrows] was an unavoidable spell, but were were poor to severely hurt Zaryusu as he honed his body through thousands of battles. Iguva=41 casted the spell again, but the lizardman took the pain and countered with a sword swing. After several rounds of this back and forth, the Traveler's movements began to slow down. His hampered movements illustrated the difference between him and the undead who knew no pain. The two combatants realized that only the strong would survive this confrontation.
Salvation came to Zaryusu from Crusch, who blessed him with [Middle Cure Wounds], restoring his vitality and erasing his pain. He and the undead continued fighting whilst Crusch and Zenberu contended with the undead warriors. To assist them, the druid summoned Snap Grasp to fight against the skeleton warriors. Crusch continued to provide support to Zaryusu and Zenberu, healing the two of their wounds to the point of exhaustion.
Zaryusu and Iguva=41 are evenly matched in their duel, exchanging blows. The lich tries to distract the warrior constantly, trying to use his concern for his friend to his advantage. But fails as the other two lizardmen have defeated his summons and urge Zaryusu to finish the fight. Iguva=41 does not wish to admit him lost as he is a creation of the Supreme Being. He then turns his attention towards the weaken pair. Zaryusu sensing his targets uses [Icy Burst], to erect a billowing freezing fog to shield his friends, but takes the brunt of the frozen vortex. Iguva=41 being an undead is unaffected but is unable to see his target, and just as he was about to cast another spell, Zaryusu leaps into the air and buries Frost Pain into the lich's skull. Though the lizardman had used [Icy Burst], the magic sword had imparted him some resistance to the cold. The blade digs deeper into the undead's cranium, finally slaying Iguva=41 ending the first part of the war in favor of the Lizardman Alliance. Zaryusu collapse after landing the final blow, but is taken back to Green Claw Village where he recuperates as the tribe celebrates.
While Cocytus felt shame at his failure he was nonetheless impressed by the lizardmen's fighting spirit and their victory. After he returned to Nazarick before the Floor Guardians and the Supreme Being to report his loss, he learned that the entire scenario was a test. The reason why he was given an inferior army to fight the lizardmen was to test his critical thinking abilities. Ainz Ooal Gown admitted that Cocytus's defeat was to teach the Floor Guardian humility. The Floor Guardian was then given command of a new army to eradicate the demi-humans to harvest their corpses for stronger undead. Hearing this Cocytus opposed this plan, and requested that Ainz spare the lizardmen and show mercy. Albedo was irritated that Cocytus would dare disobey orders, but was stayed by Ainz who allowed Cocytus to make his plea on how sparing the demi-humans would be beneficial for Nazarick.
The Floor Guardian made a case that in the future Nazarick would need to breed mighty warriors for conquest. He was confident that killing them all would be a waste and taking them as minions would yield greater results. Ainz believed he made a good point as Nazarick could always acquire corpses from the human city of E-Rantel. However, the undead from the corpses made by Ainz was more economical than using the lizardmen. Additionally, how would they vouch on their loyalty to him? Cocyus was at a loss to continue his case, until Demiurge stepped in a supplemented it with his own opinion. Demiurge advocates that in the future it may be necessary for Nazarick to use the natives of the New World. He suggested that they do an experiment in rulership, by exerting control over the natives through the use of terror. Ainz interested in the idea, accepts it. He then changes his orders from extermination to subjugation, and alters Cocytus's punishment by having him rule the lizardmen and instill their loyalties to Nazarick.
Aizn Ooal Gown then began to mobilized a new army composed of the Nazarick Old Guarders and their variant species. Combined with the Nazarick Elder Guarders and Nazarick Master Guarder their army swells to 6,000. Soon after plans are made to activate Gargantua. Preparations are made to transport their forces through the [Gate] and face the lizardmen.
Back at the lizardmen village, another undead army is spotted across the Great Lake and they notice the magical equipment that they carry. Crusch then notices that a sixth tier spell called control weather. Zenberu wonders if the "Great One" is there with them. They then watch a giant golem throw a cubed rock in the middle of the frozen lake. Then the skeletons form a staircase with their own bodies and a royal procession being formed as Ainz and his Guardians walk up to the top of the cubed rock and he sits on his throne. He sends messengers to the lizardmen asking them to send out a delegate to speak with him. Shasuryu and Zaryusu go out to meet them. They introduce themselves and Albedo orders Demiurge to make them bow down which he uses his skills to force them to bow down. Ainz then informs them that if they manage to defeat Cocytus in four hours in battle he will leave them alone. Shasuryu attempts to surrender but Ainz rejects it and leaves them after telling them that the ice will melt. He and his guardians exit by using a Gate after bidding them farewell and Demiurge releases them. After the meeting, the tribal chieftains meet and decide to call their warriors to arms but Zaryusu wants only the five of them to fight which Crusch objects to but Zaryusu talks her out of it. He embraces her once more. She then asks him to impregnate her.
At dawn and Cocytus awaits the lizardmen. To start the impending duel, the Nazarick Elder Guarders start clanging their weapons and feet in a rhythmic beat. Zaryusu, the chieftains, and several lizardmen warrior and their Swamp Elementals watch as Cocytus easily slashes several trees.
Cocytus greets them and before commencing the battle, he conjures two pillars of ice to create a makeshift gate. He declares those that cross the gate, will have their lives forfeit but gives the option for them to flee. All the elder lizardmen warriors and chieftains unanimously affirm their insistence to fight despite the odds and insist that the younger generation return to the village and live.
As the lizardmen charge at Cocytus, the Floor Guardian uses [Frost Aura] to encase most of the warriors in ice. The only ones left are the chieftains. Sukyu Juju and Kyuku Zuzu lead the attack. The former shooting at Cocytus with his slingshot while the latter continues the charge. Cocytus is protected by a shield, and thus, is immune to long range attacks. When Kyuku attempts to spear Cocytus, he is bisected by the God Slaying Emperor Blade.
On the other hand, Zenberu attempts to use his Martial Arts against Cocytus, but the monk's attacks are easily deflected. Further, Cocytus would then cut off one of Zenberu's arms. Zaryusu attempts to stab him with Frost Pain, but the Guardian catches the blade between his fingers. Cocytus uses his tail to swat the traveler away. The two lizardmen are saved when Shasuryu Shasha uses healing magic on them. Additionally, the Swamp Elementals tries to put up a fight against Cocytus, yet they end up being destroyed with a quick slash.
Afterwards, Sukyu tries attacking Cocytus again but to no avail. Seeing his attacks annoying, Cocytus uses [Piercing Icicles] and kills him. The next to fall is Zenberu when he tries to rush towards the Guardian, only to succeed in decapitating himself.
Cocytus seeing that Shasuryu and Zaryusu are left, parsing them for surviving for as long as they have. The two brother exchange words of encouragement before resuming their fight with Cocytus. Cocytus respecting his opponent asks them to declare their names to him. After the introductions are done, Shasuryu uses magic to manipulate the mud to attack him, but are rebuffed by Cocytus's defenses. Later, Zaryusu uses [Icy Burst] to cloak the area in mist. The older brother attempts to strike Cocytus with his blade and is killed. Zaryusu is the last one to attack, to which Cocytus easily catches his blade once again. However, the blade begins slipping from Coctyus's grasp. Frost Pain had been coated with blood and as it slides closer to Cocytus's chest, he declares the tactic to be magnificent. Unfortunately, the blade is blocked by Cocytus's passive ability and Zaryusu is later slain.
Once the battle finished and everything had been settled, the Lizardman officially came under the dominion of Nazarick as well as the entire southern region of the Great Lake. Cocytus became the ruler in charge in maintaining the lizardman tribe. The lizardman leaders were later revived by Ainz as part of Cocytus's wish and partly as a deal that Crusch Lulu. In exchange she would act as an inside informant that should any lizardman would think of rebelling she would directly report to him with the threat of Zarysuhu's life at stake should she betray him.