Deathstrider

In mid 2329, at the conclusion of season 3.5, several will-o-wisps, wraiths, and the like were sighted in the jungle near New Gork. A few people went to investigate these sightings and found an old town—from before the Cataclysm, it appeared—filled with various undead. Their leader, who resided in the central mansion, was identified as the only recorded deathstrider, a being of whom only myth remained.

The deathstrider was a warlock, before the Cataclysm, but sought lichdom, and although it did not entirely succeed, it became warped, twisted, to the point where records show that it at one point killed the lich who inspired it—and was still in good enough condition to fight off an army of attackers who tried to destroy it. It appeared the Cataclysm had sent it only into slumber, for it had awoken, and now threatened New Gork.

Effects on New Gork
Various undead creatures were sighted in the jungle nearby, some even venturing into the town itself and accosting the people. Casualties were kept to a minimum, however, due to a fast response. Dusk came earlier each day, unnaturally so, until the sun simply failed to rise. It was reported that after this point, the "Madness" would come, destroying the minds of anyone in the town until the deathstrider's forces could walk in unopposed.

Preliminary Mission
Four guards from the Defense Force set out to investigate the initial appearance of the undead. Word reached New Gork shortly after, through various Sendings, of their capture, escape, and subsequent recapture, along with the confirmed deaths of two of them in the escape attempt.

Second Mission
With a bit more information and preparation, an adventuring party set out with two goals: rescue any of the previous party who yet remained alive, and eliminate the threat to New Gork. The party consisted of "Doc" Dacleta, Jubal, Barb, Kalla Ormont, Núphalli Eruthúl, Nook, and Jaiyna Lifebringer. Of this group, Jubal, Nook, and Jaiyna were all lost in the final confrontation with the deathstrider. One of the guards sent on the preliminary mission was successfully rescued.

Phylactery
The deathstrider served the god known as Chemosh. The souls of those it killed were trapped in its phylactery—the deathstrider's former spellbook. Once there, they were slowly devoured by Chemosh, a process that took an estimated seven days from start to finish. Time, however, was not directly comparable between the material plane and within the phylactery; each hour that passed in the material plane was experienced as a full century within the phylactery.

Kalla Ormont was the one who unmade the phylactery, an undertaking which took two attempts lasting but a few seconds but experienced as several months as she attempted to untangle the souls still in it from their metaphysical bindings while avoiding Chemosh's notice. When the phylactery was unmade, the souls that had not yet been fully devoured were released, and one was restored to its former life—though who that was or what became of them remains unknown.

The fate of the partially devoured souls, while free of the phylactery, likewise remains unknown, although there's some likelihood that those with strong ties to other gods were pulled by those gods to their respective afterlives. Even in such a state, however, resurrection of those souls remains nigh impossible, with nothing short of a Wish spell capable of the feat.

The phylactery was successfully unmade approximately two hours after the final confrontation with the deathstrider.