The Hollows in the world ofZenless Zone Zeroare a dangerous place for any resident of New Eridu to wander in. Fully engulfed in corruption, Hollows are regulated by the Hollow Investigative Agency, an organization directly commanded by the city’s administration, the Ether gathering business lends itself to be a coveted one.

But how do HIA employees and illegally operating Hollow Raiders enter the Hollows without succumbing to the corruption and becoming an Ethereal mutant? Ether Aptitude is the key to survival.

What Is Ether Aptitude?

Ether Aptitude, as the name implies, is a measure of how good a person is at resisting corruption and how long they are able to stay within anyHollow. Being that Hollows have become part of everyday life in New Eridu, medical professionals constantly administer tests to gauge a person’s aptitude.

Since research has shown that a person’sEther Aptitude fluctuates with age, stress, and physical well-being,these tests are regularly performed on HIA employees and the city encourages regular citizens to check their with over-the-counter at-home tests.

Besides one of theattributes available for Agents, Ether is an energy source that is extracted from Hollows.

The tests are simple. The tests have a colored gauge measuring from zero to 100. The Hollow Investigative Agency and the White Star Institute research facility gauge a score of 50 or lower as not suitable to step foot inside Hollows, whilea score of over 80 is excellent and a prime target for HIA employment.

Notable Groups With High Ether Aptitude

Proxies

Amassing tons of Hollow knowledge, these contractors can guide groups of people in and out of Hollows without drawing too much attention from police or other enemies. The sibling duo known as“Phaethon”are the most renowned Proxies in the Inter-Knot.

Hollow Raiders

Hollow Raiders are Zenless Zone Zero’s version of bounty hunters.These mercenaries will take up just about any job too risky for city-contracted employees to execute.

New Eridu Public Security

As part of their duties to protect and bring criminals to justice, the New Eridu Public Security must beadept in Ether corruptionin order to enter and explore the Hollows where crime can take place.

Hollow Affairs & Neutralization Department

Not much is known about this city-sanctioned special force, but they are assigned to the toughest jobs within the Hollows, and even people with thehighest Ether Aptitudewill turn tail upon meeting with one of H.A.N.D.’s operatives.