Luden

A Luden is a special type of artificial intelligence. The Ludens are key figures in Death end re;Quest.

History
As part of their goals for world conquest, Aphesis Lane sought to create an AI being. To accomplish this, they kidnapped thousands of individuals, taking advantage of the "unused" portions of their brain functions to power a computer network capable of creating a Luden. To utilize outside expertise without alerting others to their actions, Aphesis billed the network as the "Alice Engine", a game engine capable of highly-advanced artificial intelligence.

Aggle, a major corporation secretly ran by Aphesis, would team with small-scale gaming studio Enigma Games to create a Virtual Reality MMORPG named World's Odyssey. The project, headed by bright-eyed designer Shina Ninomiya, was a perfect fit for the Alice Engine. Shina's team, including lead programmer Arata Mizunashi, worked on W.O.D. for two years. Near the end, the project was plagued with difficult and/or outright-impossible to fix bugs. Worse yet, Shina Ninomiya disappeared without a trace. These two issues caused W.O.D to be cancelled.

Shina had actually been kidnapped by Aphesis, who introduced her to the prototype Luden named Iris. Shina and Iris lived in W.O.D for a time, forming a close bond. However, at least six months prior to the events of Death end re;Quest, Shina discovered Aphesis's schemes and was murdered as a result. This caused Iris to become furious and rebel against Aphesis. As part of the rampage, roughly one-third of the kidnapped were rendered brain-dead, leaving four other Ludens in their wake: Alice, Nova, Levin, and Ripuka. Iris' body was destroyed, creating the Entoma, but Aphesis was nonetheless powerless to stop the Ludens from shutting them out of W.O.D.

The Ludens seek to accomplish Iris's goal of visiting the Shina's world. To that end, they created a virtual clone of Shina and began testing the boundaries between Shina's world and W.O.D.

Traits
Unlike the so-called AI characters that make up World's Odyssey, the Ludens are true, autonomous artificial intelligence. Alice, the de-facto leader of the Ludens, manages to write a piece of code in five minutes that Arata speculates would have taken him five days. However, Alice admits that they do not have a complete range of emotions; she encourages Arata and his party to regularly visit her and her peers so that they may learn more in that regard.

While only Ripuka is fought as a boss, it is heavily implied that the Ludens are immensely powerful, especially within the Strain Area of W.O.D.. One Death End has a Luden (heavily implied to be Nova) effortlessly split Lucil Filarete in half. While Ripuka is fought three times, the only time that the party does any meaningful damage to her is after the God of Death intervenes.

The Ludens are aware of worlds that exist outside of the bounds of W.O.D. Their plan to grant Iris's wish involves collecting data on "bugs" (i.e. supernatural phenomena) from Arata's world and using them to manipulate the Primitive Language, forcing a merger between Arata's world and W.O.D. The Ludens are also seemingly aware of the Observers, as Ripuka taunts Arata for trying to act like one. But perhaps most interesting is that it is heavily implied that the Ludens are aware that the player of Death end re;Quest exists, with "God of Death" being a title that they assigned to them. Alice addresses the God of Death multiple times, the Ripuka DLC having her do so without Arata being around; Ripuka on the other hand is openly hostile toward the God of Death, implying that she wants to kill them and even destroying the game's camera to spite their ability to watch the conflict without consequences.