Following his thorough intimidation of the Lizardmen, Lord Ains and his guardians travel to his newly-built forest stronghold. He learns it comes with a super-creepy throne made partially from human bones, and decides he’ll finally dole out Shalltear’s punishment by sitting on her.
Shalltear turning the intended pain into naughty pleasure, combined with Albedo’s violently jealous outburst in the next room, are both examples of OverLord silliness at its best. Things get even sillier when Ains uses a spell to see inside one of the village’s huts, only to catch Zaryusu and Crusch doing the nasty.
The Lizardmen elders and warriors, including Zaryusu, make their one last desperate stand against Cocytus, and are (figuratively) disarmed by his polite and respectful demeanor before being disarmed (literally), halved, and riddled with icy projectiles.
The comedy shifts from the silly to black, as Cocytus calmly, quietly explains how not a single one of his opponents’ magical or physical attacks will have the slightest effect on him; they’re simply too low a level to put a dent in his Guardian-class defenses.
That doesn’t stop Zaryusu & Co. from charging forward, even if it’s right into their grisly deaths. Zaryusu is the last to be killed, but Cocytus promises he’ll remember his name and that of his brothers as the names of warriors.
Back at base, Cocytus is praised for his victory by Lord Ains, and suggests the bodies of the dead Lizardmen be used for undead research. Cocytus makes a counter-proposal: raise Zaryusu, who had been such a valiant fighter, from the dead.
Something like that is well within Ains’ mighty means, but he wishes to make it a transaction, and so asks Crusch to spy on the other Lizardmen in exchange for the resurrection of her lover. (Her momentary assumption he wanted her body enrages both Albedo and Shalltear.)
Crusch agrees, and Zaryusu is brought back to life, and yet even here OverLord doesn’t shy away from having a bit of a laugh; Zaryusu’s speech is all high-pitched and messed-up, like he didn’t quite come back 100% right (rest will apparently restore his former gravitas).
But Ains got what he wanted: the allegiance of the Lizardmen tribes, and a mole who will alert him if that allegiance ever wavers, secured by a “spell” (in reality just a lie) that will kill Zaryusu if Crusch ever betrays him. All in all, some shrewd maneuvering by His Skullfaceiness.