In Curse Of Strahd, the Heralds of Dawn found Jassarian's burned body, and Ghalwin of the Grove accidentally grabbed his Staff of Frost; however, the party noticed in time, and managed to remove its curse. They later awakened the Lich Orlev ben Khazan, who destroyed the wizard's body and collected him to help guard the temple as an Undead guard. Jassarian was converted into a flameskull, and he eternally stalked the halls in the form of the creature who had ended his life.
Jassarian Sala-zan (translated literally to "Master Spear-of-Mist" in Scycaen, though name-meanings were more symbolic in that language) was a children of rich jewelers in Scil-Qallis, the capital and largest city of the Scycaen Imperium. Uncommonly intelligent but always somewhat devious, he trained to become a Wizard in the great city, very rarely leaving its borders. Once he had studied the Schools of Magic, however, Jassarian found that there were limits to what he could understand through scholastic pursuits. He sought to learn more practical applications of Spellcraft, and to do so, met at an adventurers guild and formed a party.
He assembled a team with the Rogue Yenduza Yunae-Maqem, Cleric of Ixhis Qiphir Harized, and a powerful Paladin of Thestus, Oxoryn Ipniani. The four went on several dangerous quests in the northern Crowncrests and the Sea of Clouds. During this time, they raided an ancient tomb, and Jassarian made contact with an unknowingly-Cursed Staff of Frost. The item made him crave power, even at the cost of his allies, and led them to taking further risky missions.
The last of such adventures occurred when they met a traveling Vistani caravan who requested their help on behalf of Kolyan Indirovich. Jassarian and the party followed Arrigal to Barovia, only to find that Kolyan was long dead; their Vistana guide then disappeared into the mists, leaving them trapped in the demiplane of the Plane of Shadow. The adventurers were experienced and powerful, however, and easily cleared the Death House after being lured in by Rose and Thornboldt Durst, then made contact with the current burgomaster, Ismark Kolyanovich.
Ismark convinced the adventurers to hunt and kill the dread lord of Barovia, Strahd von Zarovich, as revenge for "killing" his sister Ireena Kolyana. However, they group did not make it far before disaster; seeking to avoid contact with any Vistani, they headed straight for the Black Carriage Crossroads, where Strahd invited them to dinner at Castle Ravenloft. He tormented them in the castle, scrambling the party; Qiphir would die touching the Icon of Ravenloft in the castle's chapel. Strahd let them go, but only after sampling Jassarian's blood and leaving them for the Dire Wolves of the Svalich Woods.
While the three felt defeated and exposed, Jassarian was contacted by a Dark Power named Vaund, the Evasive. Believing the releasing Vaund was key to defeating Strahd, Jassarian made a Warlock pact with the entity, and occasionally used their powers to survive. The group headed down the Old Svalich Road to the Amber Temple, hiding from mobs looking to kill adventurers and Barovia's other dangers, but Jassarian was reticent to overuse Vaund's power, as he believed it would make him lose control of himself. As a result, the three generally relied on Ipniani to defeat their enemies, who had made a pact with the Dark Power Fekre and gained the ability to spread mass contagion.
After over a month, the group made their way up Mount Ghakis and into the temple proper. Jassarian employed Vaund's abilities to remain undetected by the guardian Neferon, but when Yenduza opened the doors to an armory, they found it guarded by an invisible Amber Golem. The golem broke the doors and chased them through the temple, as Jassarian desperately tried to find Vaund's sarcophagus. The noise, however, attracted Neferon, who disintegrated Yenduza on the spot; fearing death, Jassarian and Ipniani ran up the hallway, and the wizard was blown up by Flameskulls before he could escape.