Praxis is a large city located in Hollow Earth. It is sometimes referred to simply as "the underground city". It seems to be Hollow Earth's center of government and technology.
It is a vast metropolis built with materials and technology far in advance of anything available on the surface. Praxis was founded some eight thousand years ago by humans of "great and extraordinary intelligence", who fled the surface with their abnormal allies after a long war with the Akhkaru (vampires). The very reason for the City's being is to hold back the dangerous abnormals below from ever reaching the surface. If Praxis should ever fall, then Hollow Earth's dangerous abnormals would destroy everything above and below the surface. Today, the City is inhabited by both humans and abnormals who coexist peacefully and follow strict regulations established by the ruling senate. Visitors of any kind require clearance in order to enter the city limits and surface dwellers are usually not permitted entry, although a handful of surface dwellers have been permitted to enter. The metonym "Praxian" has been used to describe both the modern city and the original civilization.
The Praxians were present in many parts of the world and built numerous strongholds in their war against the vampires. They were joined by a wide variety of abnormals whom the vampires regarded as vermin. Eventually, the Praxians and their allies were forced underground, and the vampires claimed many of their strongholds, only to abandon them as their own civilization was eventually overturned.
Praxis is powered by geo-thermal energy drawn from the core of the Earth with the assistance of the Hyperspecies superabnormal known as Kanaan who is called upon by Praxis to create levees to relieve the pressure every few hundred years when the magma spikes to critical levels. The magma below Praxis is linked to three dormant super volcanoes; if the city is destroyed then the volcanoes erupt, thus causing an extinction level event on the surface.
Praxis is governed by a powerful, conservative and isolationist Senate, but much power is placed in the hands of a chief executive, Ranna Seneschal. It is unclear whether Ranna came to power through election, appointment, inheritance, or some other means, and she is described only as the city's leader. Ranna and the Senate do not always see eye-to-eye, and she has been seen to take covert action without their consent.
The rock surrounding Praxis has a high percentage of lode stone which helps with their communication network, but also acts like a natural EM shield which protects against outside hacking and prevents teleporters like John Druid from teleporting from the surface to Praxis and teleporting while in the city.
The people of Praxis have incredibly advanced technology such as organic nanite matter, and A.I. maglev transit systems, dirigibles, energy weapons and shields, and advanced holographic technology as seen with the holographic city. In the city's command center, the Praxis Garrison use holo-transfer data and neural interface devices to control communications and weapons guidance. The people of Praxis also use medical nanites and they can revive people from death by flushing their DNA with positive ions. The city also has A.I. robotic drones and chromographic sensors. The city has many storage facilities that contain weapons and anti-matter. As a safety feature, the transit system can use a holo-drill to burrow through rock if the main access tunnels are blocked. The people of Praxis have sacred laws and do not abide in unlawful transmutations so they are also capable of locking the DNA of a werewolf in order to prevent the transformation from human form. Praxis's writing system is similar to ancient Sumerian cuneiform, indicating a possible link between that ancient civilization and Praxis.
The city was founded by incredibly intelligent human refugees from the surface who lost a war with the ancient vampire civilization. The vampires made several attempts to assault or infiltrate the city, which has led to their heavy development of defensive technologies, many of them targeted specifically at vampires. The entrances to Hollow Earth are equipped with vampire detector technology which detects the presence of vampire blood by scanning those who pass through. Holographic maps recording Praxis's location utilize similar technology and cannot be accessed by vampires.
The people of Praxis are aware of the existence of Hyperspecies abnormal like Kali and Kanaan. Each of these beings has an Avatar, and together they form the Avatar Council that occasionally meets in an Avatar Chamber, which is physically located somewhere within Praxis. The Praxians have an alliance with the superabnormals and by means of a neural interface can communicate with the Avatar Council; together they maintain order on Earth, both above and below the surface.
Praxis was destroyed by Adam Worth in an attempt to power up a machine he was building to travel back in time to save his daughter's life. Exactly as the Praxians had feared, the city's destruction resulted in the Abnormals of Hollow Earth rising up to the surface; catastrophe was narrowly averted by the efforts of the Sanctuary Network.