While Krueger the Stormwrath was a boy, Mohsar saved his life when his father, a devout priest of Menoth, attempted to burn him alive after he experienced his wilding. Mohsar became Krueger's mentor and inflicted cruel savagery upon his apprentice in an effort to grind him into perfection, raze away his flaws, and elevate him bleeding and screaming to the dizzying heights of his inner potential. He once stripped Krueger and abandoned him in the desert hills east of Acrennia, forcing him to return using his own strength and cunning. According to Krueger, every day spent with Mohsar had been a lesson in enduring torture both mental and physical.
In 608 AR, Mohsar puts aside his isolation, troubled by the skorne, who meddle with things they do not understand. Soon he receives news that Krueger has recently stolen the Wyrmstone from Dahlekov, which details the alliance of dragons against Lord Toruk in 1000 BR. When Krueger asks him for a meeting request, Mohsar accepts, and appears as in the form of a mirage in front of Krueger.
Mohsar warns Krueger he has chosen an opportune time to defy the Circle, though it is unlikely Mohsar will be in a position to reprimand him personally yet. Krueger asks Mohsar of Everblight's name on the Wyrmstone and of the dragon who organised the alliance. Mohsar replies Everblight did not participate in the alliance, which was organised by Blighterghast, and demands his apprentice to waste no more of his time before cutting the connection.
At the skorne-occupied Castle of the Keys, Mohsar discovers the very existence of a skorne called Void Seer Mordikaar is anathema to the natural world, like an infected boil on the body of Orboros, and the unnatural spirits the aberrant scholar pulled to Caen are like a cancer. That the skorne discovered a way to exploit dragon blight to augment this process made the situation all the more alarming. Mordikaar has remained isolated deep within his well-fortified laboratory, and Mohsar begins to expect he would need to gather a sizable army to make an overt strike on the fortress.
While Mohsar watches the fortress like a patient spider, he spots two dragons - Halfaug and Scaefang - approaching the Castle of the Keys, killing many skorne defenders. He feels surprised awe, never expecting that his former apprentice’s maddening arrogance might succeed in stirring the dragons from their centuries of inaction. For a moment Mohsar hopes the dragons might kill Mordikaar for him, unfortunately they do not prove so cooperative.
After the dragons leave, Mohsar suddenly raids the fortress with his wolds and manage to corner Mordikaar. As he prepares to kill the void seer, Mordikaar warns Mohsar his death will bring out a disaster enough to destroy Mohsar, and to warp these lands beyond recognition. Mohsar then opts to capture Mordikaar alive instead of killing him, but the arrival of Dominar Rasheth forces him to retreat.
A short time after, the potents and omnipotents of the Circle gather in the Grand Conclave Tribunal in the Wyrmwall Mountains, except for Krueger and Baldur, who is currently unable to attend. The matter at hand is an accusation of fomenting insurrection and turning traitor, levied by Dahlekov against Krueger. Dahlekov rests his case: Krueger stole the Wyrmstone, gathered his army, clearly bent on usurpation, then defied Lortus' restriction against initiating contact with Blighterghast. Mohsar agrees with Dahlekov, though surprisingly Lortus speaks in defence of Krueger. Since the omnipotents are not in accord, Mohsar asks the potents for their consensus - per ancient laws, the penalty of death for a potent requires a sublime majority. After all the potents voice their agreement, Mohsar declares the majority achieved, judges Krueger guilty, sentences him to death and volunteers to carry out the sentence, though Dahlekov tells him that's not necessary.
As the potents prepare to disperse, Wurmwood suddenly appears with Cassius the Oathkeeper. Cassius affirms Krueger is no traitor to the Circle - the Tree of Fate has the right to offer opinion when the omnipotents are not in unanimous accord. Morvahna the Autumnblade speaks in defiance of Wurmwood, but since Wurmwood's vote has greater weight than that of the collective potents, Mohsar warns her to not force him to strip her rank, then declares the sublime majority broken and the sentence rescinded.
Returning to his dominion, Mohsar finds a skorne army led by Void Seer Mordikaar attacking a group of blackclads conducting a rite in the Bones of Orboros. Quickly teleporting with two Celestial Fulcrums into the site, Mohsar reaches into the ley line nexus and banishes Mordikaar and his nearest allies, hurling them through the connected nodes deep into the desert to the southeast. Mordikaar is gone, but one of their sites has been sacrificed. Mohsar then opens a chasm in the earth, killing the majority of the skorne forces and prompting the rest to flee.
Discovering the rite was being conducted by Morvahna and Baldur, who is still alive, Mohsar reproaches Baldur for not asking permission from him. Baldur says he cannot risk Mohsar's refusal and asks Mohsar for his power if he fears the leylines could be damaged by Baldur's failure. Mohsar helps Baldur and Morvahna finish the rite, and Baldur assures him the ley lines will heal in time. As the skorne return, Mohsar quickly teleports the Circle army away.
After the battle, Mohsar sends Bradigus Thorle to the Pillars of Rotterhorn to assess and repair the damage done to the ley lines. Noticing a significant drain in the energy from both the Southern and Eastern Dominions, he initially suspects Krueger until Thorle informs him of Wurmwood's involvement and a gatorman army suspected to be preparing for a great ritual. Sensing Mordikaar heading for one of the skorne's holdings at the southern border of Ios, Mohsar moves through the ley lines to the northern Bloodstone Marches, towards Mordikaar.
Mohsar emerges to find the Tharn king Kromac claiming Rathrok from its previous wielder Madrak Ironhide and the Devourer Wurm manifesting through the portal to Urcaen accompanying Mordikaar. Mohsar warns Kromac to leave, then seeks out the trollkin shaman Hoarluk Doomshaper. Together, Doomshaper, Mohsar, and the accompanying druids start to banish the Wurm back to Urcaen. The Wurm's power overwhelms the junior druids, two woldwatchers and a celestial fulcrum, until Dahlekov and Lortus arrive, and with their help, the Beast of All Shapes is forced back to Urcaen.
Mohsar's loathing of humanity is legendary, and even his fellows he tolerates only when absolutely necessary. Any army he calls to battle is disposable, a force to be spent toward his ends. Despite the callousness of his approach, the allies of Orboros fear him too much to refuse his summons. Mohsar is as relentless as the sun and emanates scornful disregard as palpable as the hot wind blowing across the dunes.