Zerns are a species that many humans wonder if they should be classified as heteromorphs. However, since Zerns can be affected by spells that worked on demi-humans, so they were classed as the latter. But in fact they truly are heteromorphs.
They were one of many races that Jaldabaoth enslaved as part of his demi-human coalition to attack the Roble Holy Kingdom. Their allegiance to the Demon Emperor was under duress, as the demon held their leaders hostage to secure their cooperation. They aided the alliance in its takeover of the Northern Holy Kingdom. While they followed Jaldabaoth's orders, they secretly despised working under the monster.
When word reached that their king was executed on Jaldaboath's orders, Zern decided they had enough. To secure the last remaining royal the Zern reached out to the Holy Kingdom Liberation Army pleading them to rescue Beebeezee. While they did not wish to join forces with the humans against the Demon Emperor and his allies they swore that the Zern would pull out from the war depriving the Demi-Human Alliance of 3,000 able soldiers.
After Prince Beebeezee was rescued, by Neia Baraja and CZ2128 Delta, 2,800 of them had gone with their prince to the Sorcerer Kingdom, while the remaining 200 or so had gone to the hills to collect information. At the most critical point of the war, the Zern alongside other demi-human races were seen part of an army that came to the rescue of the human resistance.
Zerns are a slimy species with whose upper bodies are like eels with arms and whose slimy lower bodies are like blue-colored maggots. They are a sexually dimorphic race, females possess blue skin while the rare males are much smaller, possess purple skin and no arms.
Zerns have the racial weakness of being affected by race-specific spells, so people have mistakenly classified them as demi-humans when they are in fact heteromorphs. In addition Zerns are colorblind due to the fact their species adapted to environments with low level light.
Even if all the male Zerns were wiped out, there were cases where females could change sexes.
The Zerns are similar to insect communities, and live in hives beneath the surface of the Abelion Hills. Zerns are born from eggs, as hinted when they refer their comrades, as "eggmates". Males within the Zern species are few. On occasion when a new one is born, they instantly become royalty. Life of a royal is mostly secluded with one never leaving the nest to the end of his life.
The Zerns mostly feed on precious bodily fluids of living creatures, be they alive or dead. The Zerns also are cannibals, eating their dead or others in respectful fashion, it also serves as their official way of mourning.
The Zern calendar system is based on the four seasons, each with at least 98 days.
While most of the relationship with the other inhabitants of the Abelion Hills is unknown, however at least one other species the Pandex seemed to have had good relations, due to similar cultures although inter-species relations seems to have been seen as a taboo.
- To prove a point of his ruthlessness, Jaldabaoth tore the Zern representative's shoulder after he breached the Great Wall of the Holy Kingdom.
- Due to the Zerns' appearance, they are sometimes give the nickname called "Blue Maggots" in relation to it.
- They are the first New World Heteromorphic race Ainz has encountered that have an established form of civilization and culture.
- The Zerns are the first race in the Demi-Human Alliance to rebel against the Demon Emperor.