Demons are separated into different types (sub-species, almost) 
called Bands. Likewise for angels, who are in Choirs. Each Band 
corresponds to a Choir - a Seraph Falls to become a Balseraph, a 
Balseraph Redeems into a Seraph (The exception is Malakim, who cannot 
Fall, and Lilim, who are all born in Hell). 

Each Choir and Band has its own special resonance (an ability that's 
part of its nature), but becomes dissonant if it betrays that nature. 

Choirs and Bands heavily influence character you're going to be 
playing. It's In Nomine's version of character classes for 
celestials, almost. 

A brief run down of the characters' Bands. 

Balseraphs: The lowest Band of demons. The Liars, aka Serpents, are 
demons of deception. Their resonance allows them to convince others 
that what they say is the absolute truth, and if the victim cannot 
resist, he'll believe the Balseraph for at the very least, one 
minute.  Of course, no one's going to believe the sun is really the 
moon, but opinions and any fact that can't be proven by concrete 
evidence are fair ground for the Balseraph resonance.  
Balseraphs take dissonance if they contradict themselves while the 
victim still believes the lie.  Also, should the would-be victim 
succeed in resisting, the Balseraph will take dissonance from that 
one-sixth of the time.  Wrapped in lies, paranoia, and selfishness, 
angels hate the Balseraphs most out of all demons.
Balseraphs appear Celestially as leather winged, six-eyed serpents of 
various sizes, shapes, and colours. Balseraphs redeem to become 
Seraphim, the Most Holy Choir of similar-appearing angels who can 
resonate to determine the Truth. 
Amariah/Ambrosius is a Balseraph.

Lilim: Created after the Fall by Lilith, the Princess of Freedom, the 
Tempters are all Hellborn.  A Lilim can look into someone's eyes and 
identify his deepest desires.  If the Lilim then fulfills the Need, 
she can receive a geas-hook at a level depending on how pressing the 
Need was in relation to the person receiving it.  The Lilim can then 
impose a Geas of the same level on the victim, forcing him to 
accomplish a task in a certain amount of time, or to waste away until 
he does.  Lilim take dissonance if they fulfill a person's Need and 
their attempt to call the favour in fails.  If they fail twice at an 
attempted Geas, they lose the geas-hook forever.  They can also Geas 
themselves into doing tasks, which are highly sought out by other 
demons, as a Lilim cannot escape her own Geas.
Lilim understand Honour, but because of the propaganda in Hell about 
the horrors of Heaven, few Lilim ever try to redeem.  If they do, 
they become Bright Lilim, having no corresponding Choir of angels to 
join.
When Lilim are created, they can either choose to bind and serve a 
Prince, or become Free Lilim.  Free Lilim start off with 9 Geases 
owed to their Mother, who frequently trades them to other Prunces. 
Free Lilim usually spend their existence trying to escape their debt, 
making the concept of "Free Lilim" a cruel joke.
Celestially, Lilim appear as their Vessels, with green skin, horns, 
and without wings. They usually wear metallic Geas-bands (gold, 
silver, iron), marking the debts they owe. 
Diamante/Jesse is a Lilim.

Shedim: The most disgusting of demons.  The Corruptors are demons of 
dark possession.  A Shedite can possess a human, gaining access to 
all of his thoughts, feelings, and memories, and force the human to 
degrade himself.  
Humans possessed by Corruptors frequently never realize it, instead 
fooled into thinking they came up with the Shedite inspired urges.  
It is dissonant for a Shedite to go for a day without pushing a host 
to corrupt himself, but they also gain dissonance if their host dies 
with them still in it.  Because the Shedite and the host vie for 
control of the body at stressful times, most Shedim focus on quick 
and easy evil.  They owe the most to Lucifer, and promote the evils 
of Satanism in all forms.  They are despised by the Lilim, who feel 
they give demons a bad name.
Shedim Redeem to become Kyriotates, similar angels with a resonance 
for multiplicity.  A Kyriotate can possess several hosts while a 
shedite can only possess one, but a Kyriotate does not gain access to 
their memories.
Celestially, Shedim appear as revolting black clouds of limbs, wings, 
eyes, tongues, and other unidentifiable organs, pulsing to a mad, 
infernal beat.
Zha'an is a Shedite.

Habbalah: Also known as Punishers, a Habbalite is firmly convinced,
despite overwhelming evidence, that he is in fact an angel, sent
to work in Hell to punish the weak; the fact that he can't go to
heaven is overwritten - after all, the Wimp Angels up there can't
handle Hell, and somebody has to.  Habbalah are projective empaths
- they can throw their emotions onto someone, and at a penalty can
sense emotions - but it is dissonant if their resonance rebounds 
when the target rolls a high CD (Check Digit).  They can choose to
absorb the rebounding emotion instead of taking dissonance - so a
Habbalah who tries to throw Angry and has it rebound will suddenly
fly into a fury.
Habbalah redeem to become Elohim when they think to Redeem, which 
isn't often - after all, they're already angels, right?
Celestially, Habbalah appear as scarred, mutilated, and heavily 
tattooed Elohim.  All Elohim appear identical, and a Habbalite
fanatically reclaims its identity by carving one into itself.
Melaine is a Habbalite.

All Demons, save Free Lilim, who are traded between Princes 
endlessly, serve a Demon Prince and a Word - a concept fighting 
against the Symphony.

The Demon Princes involved in DGC! are as follows: 

Kobal, Impudite Demon Prince of Dark Humour: Irony, scorn, and 
mockery make up Kobal's word.  Kobal was the Angel of Laughter, but 
he rebelled in the original Fall.  Recently,  Kobal has found himself 
bored with Earth.  He's finding less and less worth laughing at.  His 
servitors enjoy a good deal of freedom, being left to their own devices 
on finding creative ways to mock the Symphony.  It is 
dissonant for Servitors of Kobal to go a day without making someone's 
life more miserable, either by laughing at him or making others 
laugh.  All three of the PCs serve Kobal.

Nybbas, Impudite Demon Prince of the Media: Nybbas is the most recent 
Prince of real power to be appointed.  He was a lowly servitor of 
Vapula, when in the late 19th century, he invented the television, 
and Lucifer appointed him as Demon Prince of the Media.  In that 
time, Nybbas has established a firm base on Earth, and runs a very 
ambitious organization that never stops.  It is dissonant for 
Servitors of the Media to not spend at least an hour a day 
contributing to the growth of the Media.  Several NPCs serve Nybbas.

Kronos, Balseraph Demon Prince of Fate: Kronos is the most powerful 
Prince in all of Hell.  His servitors can still interact with the 
Symphony, and strive to make mankind give in to its most base 
impulses and succumb to its horrible dark Fate, as opposed to its 
Divine equivalent, which is Destiny.  Kronos' classification as a 
Balseraph is not true; he belongs to no Band and is in fact a dark 
opposite of the Archangel of Destiny who appeared after the Fall.  It 
is dissonant for Servitors of Fate to help a human attain his 
Destiny, or taking action to prevent a human from meeting his Fate.  
The PCs strive to thwart a plan of Fate.

Vapula, Habbalite Demon Prince of Technology: Vapula attained his 
position as a Prince during the Industrial Revolution.  With no clues 
as to how technology is ordained to unfold in the Symphony, Vapula's 
servitors are forced to experiment, creating weird and dangerous 
pieces of equipment.

Asmodeus, Djinn Demon Prince of the Game: Asmodeus was once a 
servitor of Judgment, but he rebelled in the original Fall.  His role 
is to police the forces of Hell, routing out Renegade demons and 
keeping the others in line through intimidation, tyranny, and 
torture.  He is an ally of Kronos, and immensely hated by Kobal.

Andrealphus, Impudite Prince of Lust: Once the Archangel of Love, he 
Fell with many others after Lucifer 'proved' to him that Love didn't 
exist.  His servitors spread Lust throughout Earth, sex without 
caring.

Now, the PCs: 

Amariah, Balseraph of Dark Humour: Arrogant, smarmy, and somewhat 
reckless, Amariah is a Fallen Seraph with at least some intimate ties 
to Destiny.  He gets immense joy out of annoying other people, 
especially angels, and is constantly thinking up new and usually 
risky plans for their mission.  Amariah's devil-may-care attitude has 
even provoked a fellow demon into attacking him, and gotten him a 
caution from his Prince to be less obvious.  Will he be able to 
smooth out the rough ends in his relationships, or will he go too far 
and wind up dead?  And if the latter, at whose hands?

Diamante, Free Lilim in service to Dark Humour: Diamante is a 
Daughter of Lilith who has taken a male vessel.  He's been certified 
as "Honourable" by some angels, but is absolutely terrified at the 
prospect of Redemption, though he seems to have some knowledge about 
angelic things.  The most sensible of the group, will he hold onto 
his freedom, bind, or overcome his fear and join the angels? - note,
question answered.  Joined the angels.  Now an NPC.

Zha'an, Shedite of Dark Humour: Hellborn demon, Zha'an is a Shedite 
who revels in driving his hosts toward evil.  Zha'an's ability to 
abuse hosts has earned him the role of dealing with situations that 
shouldn't be traced back to the group, as he can always find a new 
host in a crowd.  It's crude antics combined with an almost sensible 
manner make Zha'an quite the contradiction.  He's attacked Amariah 
once, will he hold the party together, or shake it apart? - note,
question answered. Shook the party apart when he Redeemed to Flowers.

Melpomene, Habbalite of Dark Humour: Jesse's 'replacement', Mel is
a Punisher who seems to have a cool, underhanded sense of humour and
an even temper.  He also claims to be Thalia's sister, and vice 
versa.  Little enough is known about him, or the 'pseudonyms' Thalia
made reference to...