The Three Celestials' Roles
Ophanimon's official profile defines the division of the trio guarding the Kernel: Seraphimon is the unforgiving Marshall of God (the law), Cherubimon the steadfast defender of God and wisdom, and Ophanimon the merciful and compassionate side, the holy mother of the Digital World.
Ophanimon, the Fallen Goddess
Lilithmon's official profile says it is thought to have once been an Ophanimon that fell from grace, becoming the Goddess of Darkness. A perfect mirror of Seraphimon and Daemon: two of the Three Celestials have a Demon Lord as their fallen counterpart.
Rasielmon, the Ophan Among Soldiers
Rasielmon once held the same rank as Ophanimon. It keeps the Ophan rank and the ability to look out on the entire world from the Kernel, having built up the knowledge of a god, but it no longer holds a Celestial seat and serves alongside the army instead.
Dominimon, the Phantom
Dominimon does not answer in any way to the angelic chain of command: it manifests via mutation when the balance of light and darkness breaks, is almost never sighted, and only joins ClavisAngemon and SlashAngemon against extreme threats, sacrificing its own lifeforce (Devotion Field).
ClavisAngemon and the Zenith Gate
ClavisAngemon guards the Zenith Gate, sealed by 360 doors between the Digital World and the outside, holding The Key, a master key only it can wield. Some suspect the Digimon itself is part of the key, whose power could collapse the Digital World.
A Power Leads the Army
SlashAngemon's official profile confirms it commands the Angelic Army (Powers). In classical angelology the Powers are precisely the warrior angels, so an army led by a middle rank rather than a Seraph is faithful to the original hierarchy.
The War Against Millenniumon
In Digimon Adventure: (the 2020 reboot), Seraphimon, Ophanimon, Cherubimon, ClavisAngemon, SlashAngemon, Rasielmon and Valdurmon fought Millenniumon together in the distant past: the only time most of this roster takes the field as an actual army.
Three Falls, Three Stories
ShadowSeraphimon is officially Seraphimon swallowed by darkness as its concealed resentment swelled, and is said to fall into an Evil King Digimon if it keeps this form too long. Cherubimon (Evil) is born in Frontier: feeling betrayed by Seraphimon and Ophanimon, it was corrupted by Lucemon. Ophanimon Falldown Mode is an Ophanimon so angry it suppressed its own emotions and fell into madness; in Adventure tri. it is born from Kari's despair and fuses with Raguelmon into Ordinemon.