Unique Boss Monsters, commonly abbreviated as UBM, are a classification of monsters in Infinite Dendrogram.
Information
As the name suggests, Unique Boss Monsters is a classification granted by Management A.I No. 4, Jabberwock to 'boss' monsters that, due to the way they were born or created, can never be replicated ever again, making them in effect completely unique existences. As such, their name (if they have one) and a title are applied to the status visible to Masters. Along with their unique nature, UBMs possess great strength and unique abilities, to the point where they can be referred to as the 'Masters' of monsters.
Creation
A UBM can be 'created' in a variety of ways. Management A.I. No. 4, Jabberwock can, by use of the *** function, transform an ordinary monster into a UBM, granting them increased strength, intelligence and unique abilities, if they are able to withstand the process. A monster which was unique from birth/creation and possessing unique abilities can also be granted the title of UBM, as long as they are not someone else's possession and/or created to be used as a tool for others.
Special Rewards
When a UBM is defeated, Jabberwock will select an MVP (Most Valuable Player) from the participating fighters and convert the resources of the slain UBM into a unique drop item for them. This drop item will be customized to be exactly what the MVP needs (in Jabberwock's view). This can range from the complete remains of the monsters, to be processed by a production class job holder into a new monster or an item that possesses the ability of the UBM.
Types of UBM
UBMs can be separated into different classifications based on a number of different factors, such as combat ability, level, etc. These rankings are Epic, Legendary, Ancient Legendary, Mythical and Superior. There is also an informal ranking known as "Irregular."
Epic
The lowest ranking of UBM. Generally speaking, it is thought that it would take someone with a high rank job and high rank Embryo to defeat a monster in this class. However, due to the differences in potential abilities between monsters, the strength of those in this class can vary wildly.
Legendary
The 2nd lowest ranking class of UBM. Generally speaking, it would take a quasi-Superior (someone with a Superior Job and an Embryo in the 6th form) to defeat a monster in this class. For a Superior however, defeating a monster of this class is not usually a difficult task. Because a monster of this level is difficult to defeat for a tian with a Superior Job, defeating a UBM of this class can become a national level project.
Ancient Legendary
The intermediate ranking class of UBM. At this level, even a battle type Superior would be hard pressed, with only a 30% chance of victory. They can be classified into various types, such as the pure performance type with extremely high stats, the multiple skill type boasting many different skills, or the skill specialized type, which sacrifices performance in all other areas to boost a single skill to the highest level. If the compatibility is bad, even a Superior would be unable to defeat this type.
Mythical
The upper rank class of UBM. They possess extreme power, to the point where a battle type Superior would find victory extremely difficult.
Superior
The apex of the UBM. These are non-standard UBMs that have surpassed Level 100. Only monsters of this level that can be reliably controlled by the control A.I.s are given this designation. As such monsters are few and far between, they were collected and stored before Infinite Dendrogram began, to be used to create artificial disasters which would force the evolution of new Superiors. In terms of strength, they are powerful enough to destroy a country, and require multiple Superiors working in concert to defeat. They were not known to exist until the Greatest One was seen in the Dryfe Imperium. Unusually, it is possible for SUBMs to give multiple special rewards, a phenomenon thought impossible beforehand.
Irregular
An informal category, given to a UBM that has surpassed Level 100, but cannot be controlled by the control A.I.s They are registered in the system as Mythical UBMs, but possess power equal to that of SUBMs. As such, before the start of Infinite Dendrogram the A.I.s themselves would sortie to destroy them whenever they appeared. After the game began, the policy was changed to limiting their actions or in the worst case, manipulating Superiors to deal with them. However, some irregular UBMs were left alone by the Management A.I.s for various reasons. Currently, there is an irregular UBM dwelling in each of the seven countries.