Orb Vallis

 The Orb Vallis is an open-world region on Venus. This land of duality, where cold tundras made by Orokin terraformation devices mix with the original harsh Venusian atmosphere, is home to multiple Corpus outposts and colonies, among them the debt-internment colony of Fortuna. It is also home to the Raknoid family of proxies, the larger Orb models of which serve as bosses. 

General
The Orb Vallis is a massive expansive area featuring various fields, hills, caves, and bodies of water in a snowy climate. Unlike other mission nodes, Orb Vallis is not procedurally generated using Tiles, but is instead a massive static map with unique features.

Orb Vallis is accessible through two different mission nodes on the Star Chart on Venus. The first is the central hub of the Vallis – Fortuna – where the player will spawn in a plaza located within the underground city. The second mission node will spawn the player directly in front of the elevator that connects Fortuna to the Vallis.

Each server instance of Fortuna can hold up to 50 players within the town, however players can only exit onto the Vallis in the standard 2-4 man squads or Solo. Each map is considered its own separate mission instance, and will not be shared between squads.

Entering into the Vallis from either Fortuna or directly from the Star Chart will create a new mission instance of the Vallis, with procedural generation applying to objects like resource spawn locations and mineral veins, as well as assigning a random Challenge.

Progress on the Vallis is saved under the following conditions:
 * Upon returning to Fortuna through the elevator at any point, with the mission concluding and all progress saved.
 * On returning to the player's Orbiter via the escape menu.
 * All progress is automatically saved on completing Bounties or Incursions.
 * Fishing, Mining, or using consumables results in a specific save of that content (fish caught, minerals extracted, consumables used).

Fortuna
Fortuna is an underground settlement that is home to the Solaris, a population of mechanically-augmented people who work as debt-slaves for the Corpus under Nef Anyo to bring the ancient Orokin terraformation devices on Venus back online. This town serves as the central hub for Orb Vallis, where players can interact with various NPC's to purchase items from shops, or accept quests to be accomplished out in the Vallis.

Upon arriving on Fortuna, players are deposited on a plaza by the center of the settlement near a large artificial river of coolant. From there, players can exit Fortuna onto the greater Vallis via a large door on the town's edge, leading to an elevator that will bring players up to the Vallis outside. The elevator acts as a loading screen, and players will be unable to exit out the other end until the loading is complete.

Trivia

 * According to Steve Sinclair, the creative director of WARFRAME, the visible change between the day-night cycle of Orb Vallis is caused by an orbiting terraforming reflector.