The Digital World of most anime series, governed by the host computer King Drasil. Its knights take their name from medieval chivalry and its host, Yggdrasill in Japanese, from the world tree of Norse myth, while holy beasts of Chinese cosmology guard its compass and an ancient war still echoes through its history.
the ordinary Digital World, as official material calls it
Official material calls this world simply the Digital World: Digimon Profile #035 calls it the ordinary Digital World beside Iliad, and the Shambala page counts Shambala as one more world after the Digital World and Iliad. The atlas calls it Classic to tell them apart. King Drasil, the mysterious host computer, governs the entirety of the Digital World on the Network. The Royal Knights are the highest rank of network security under its jurisdiction: King Drasil apparently selects them, and each knight interprets its orders for itself.
The world's identity is mixed. The host computer is named after the world tree of Norse myth and the knights draw on medieval chivalry, but the Four Sovereigns and their Deva come from Chinese and Buddhist cosmology, and the Ten Legendary Warriors belong to an ancient era of their own.
main guardian organization: the thirteen Holy Knights
Said to number thirteen, the knights are the highest rank of network security in King Drasil's Digital World. Each one interprets King Drasil's orders for itself and solves problems its own way, so at times the knights disagree to the point of fighting one another, and at times they cooperate. Alphamon, the Lord of the Empty Seat, is said to act as a deterrent to the other knights and usually stays hidden.
OmnimonHoly Knight
AlphamonLord of the Empty Seat
GallantmonHoly Knight
MagnamonHoly Knight
UlforceVeedramonHoly Knight
DynasmonHoly Knight
CrusadermonHoly Knight
CraniamonHoly Knight
KentaurosmonHoly Knight
LeopardmonHoly Knight
ExamonHoly Knight
GankoomonHoly Knight
JesmonThirteenth seat
secondary organization: guardians of the compass and their twelve generals
Four Holy Beasts that have protected the Digital World and governed its stability since the age of myth, each ruling a compass point and commanding three of the twelve Deva. Huanglongmon, the emperor of the Center, once ruled them, until an Angel Digimon sealed it deep underground in ancient times; without their ruler, the four struggled for supremacy before settling into today's balance. They are not subordinates of the Royal Knights: no official text ranks one group under the other.
historical group: the saviors of the Ancient Digital World
Ancient warriors, one per element, who saved the Ancient Digital World and are said to be among the first Mega Digimon. AncientGreymon and AncientGarurumon survived the holy war to the end and are said to have sealed Lucemon, and the warriors' power lives on in twenty Legendary Spirits. They belong to the world's distant past, not to its present government: no official text places them under King Drasil or the Royal Knights.
AncientGreymonFlame
AncientGarurumonLight
AncientBeetlemonThunder
AncientKazemonWind
AncientMegatheriummonIce
AncientMermaidmonWater
AncientSphinxmonDarkness
AncientTroiamonWood
AncientVolcanomonEarth
AncientWisemonSteel
the Classic world's underworld, guarded and judged by Anubismon

Established Lore
Anubismon guards and supervises the Dark Area and acts as the judge of the Digital World. Its profile says it seals Digimon made of evil data away in eternal darkness and lets Digimon made of good data be reborn as Digi-Eggs; Digimon Profile #035 adds that data judged bad keeps wandering the Dark Area.
Anubismon is a guardian and a judge, not a sovereign. Official material gives every Digital World its own Dark Area, and nowhere calls Anubismon the ruler of all of them. Below this Dark Area lies Cocytus, the single deepest layer shared by every world.
who answers to whom, and how firmly each link is established
Names link to DigimonWiki/Fandom (CC BY-SA unless noted otherwise); artwork © Bandai, shown from the official Digimon Reference Book. The atlas is an editorial model built from official material, not a universal chain of command. King Drasil and Anubismon are Yggdrasill and Anubimon in Japanese material, and Huanglongmon is DigimonWiki's name for the official Fanglongmon.