Nemortsi

The most powerful kind of undead. They are often able to appear to be alive, or they are unspeakable monstrosities with power over other undead. Or both.

Necrarach

The massive, bulbous arachnoid monstrosities that are crafted out of a follower of Ettuttu and a giant spider that are the hierarchs of Srisia. It is unknown if they can even be destroyed, and no one has ever seen one outside of a single chamber in Srisia where the Srisian Church keeps them sealed away as an undead hall of saints.

Grey Lord

Warlords who committed atrocities in life and used them to turn into undead masters who could raise their victims into an army of ruthless killers and bringers of horror. They are very rare and extremely dangerous, but the few who have existed were said to have been destroyed only by the united efforts of at least 13 and usually more wielders of celestial or elemental magic.

Deus Mors

Those who made a deal with a demon to become undead and gain immense infernal power, these "death god"s command lesser demons and undead. They are part necromancer, part demonologer. They are feared in the Hells and in the mortal realm, and none have ever recorded destroying one, only sealing them away with extremely powerful celestial or elemental magic.

Bash Tchelik

An undead figure that puts its life into a secret place, allowing it to live on, appearing alive but full of powerful undead magic. Similar to a lich, but based on folklore. They are only destroyable if the thing they have hidden their life in (a soul jar, though rarely literally a jar) is destroyed.

Grey Saint

A follower of the goddess Olumsuzluk who has been canonized and returned as a saint with enormous power. They can only be defeated by a faith stronger than their own.

Koni

A monster made of the souls and bodies of 1,000 drowned children, turned into a tentacled, undead monstrosity of the deeps. Calling the names of all 1,000 children where the koni can hear it will send them away.