Bumping for interest.

I thought it would be better to give some basic ideas about how certain pantheons work and how they get their piece of business. This goes for human non-mage, human mage, pantheon, demon, and fairy factions. This is sort of a working rogue's gallery of some of the most egregious instigators and some of the closest allies.

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[*] [b]The Mount Olympus Pact[/b]: While sixteen pantheons signed and fiscally support the Infernal Intervention Team, Mount Olympus is one of four active supporters and suppliers for the team as far as pantheons go. Primarily encompassing the Greco-Roman gods and led by the Olympians, this faction raises their kids to become members of the team. While some of them have fallen from grace and some even became instigators of incidents requiring action from the II Team, the majority have grown up past their early, pettier days and become a rational body.
[*] [b]First Nation of the Duat[/b]: The animal, desert realm of the Egyptian Gods is another of the four active supporters. Formerly lead by Ammun-Ra, currently the throne is split between Queen Isis and King Horus and they are famous for their imbuing powers to those who seek justice and having a high standard for spiritual purity, either giving impure souls to underworld pantheons or destroying the consciousness and using them as fuel. 
[*] [b]Valkyrie[/b]: The warlike Norse gods of their own agency Valkyrie act as the third primary contributor from the pantheons. Led by Freya after the disappearance of Thor, Valkyrie offers up soldiers to aid in conflicts that could potentially lead to an end-of-Valhalla class scenario.
[*] [b]The Heavenly Host[/b]: The fourth and most powerful of the direct supporters of the Infernal Intervention society, and while one of the most outwardly beneficent factions in all of the multiverse one that has a very dark and shady history. Their eons-old ruler, who currently claims the moniker of Leon Shaddai, was a fierce and terrible god who boasted power and absolute control over his people. It wasn't until thousands upon thousands of years later that he mellowed out, and in his relations campaign he used diplomacy and kindness to build up a vast empire that triumphs over most of the Western Hemisphere and many parts of Europe and East Africa. His prior history and the fact that, due to his large faction being split up into separate denominations, some factions don't hold to tightly to his more recent ideals and don't receive punishment make the alliance with him seem shaky and earning his ire seem like a very, [i]very[/i] bad idea.
[*] [b]The Western Mages Guild and Goodwitch[/b]: An organization comprised of the classical ideas of wizards, mages, and witches. It's more of an overall governing system for dozens upon dozens of mage guilds and wizarding schools and clans of magically adept humans in the face of a world that has grown to learn about them. There are a few factions that are just as big that lie outside of them, but the majority of wizards come from here.
[*] [b]Treeshapers[/b]: Summoners, Vodun practitioners, and elemental druids largely come from here. Basing their magical systems off of the Celtic and Germanic systems of magic, they utilize runes, thaumaturgy, and the ability to befriend elemental creatures in order to exact change. Many times there are contracts made between elementals and members of the Treeshapers, and they end up becoming one being with the consciousness shared 80% human, 20% elemental.
[*] [b]The Balance[/b]: Coming completely out of nowhere but an important part of the setting are these warrior monks. These monks follow the Chinese, Hindu, Shinto and Confuscian principles and their power comes from learning to master manipulating and changing just one force. It could be heat, friction, gravity, or a small ability like that, and calling it forth from their hands, and using that one concept to its absolute fullest potential. The most powerful of them who become Grand Masters are on the level of some of the pantheons' kings, but to attain such a title takes decades. With physical longevity and mental security, they are devout in their principles and seek to attain balance, never seeking more power for themselves than is offered to them by change.
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[*] [b]The Infernal Empire (Hell)[/b]: The upgraded, far-reaching version of old Judeo-Christian Hell. Its hierarchy of demons and former gods ranks in the tens of thousands, with the entirety of Hell divided Mafia-style into several main branches subdivided into families. Each have different goals and means, with some corrupting souls to claim later, some being in charge of deal making, some in charge of keeping tabs on or sabotaging competition, and some involved in killing and reaping souls through warfare or destruction. While leadership has changed to be regulated by a ten-demon council known as the Infernos, the individual clans and especially families are usually not given any punishment for their actions. Major clans include: The Goetian Clan, whose forces include families Belial, Ba'al, Asmodeus, and Paimon among others; The Verum, whose forces include families Satanachia, Agaliarept, Nebiros, and Syrach among others; the Oberonica Clan, whose forces include families Egyn and Spyrion among others; the Nuctemeron Clan, whose forces include families Hahabi, Eglun, and Tarab among others; the Grigori Clan, whose forces include families Yeqon, Gadre'el, and Samyaza among others; the Sephiroth Clan, whose forces include families Samael and Lilith among others; and the Chthonic Clan, whose forces include families Verrine and Oelliet among others. This faction is responsible for between 40%-60% of all incidents that require the II Team's action. Not all of the Infernal Empire's forces are completely bad, and allies within the organization are some of the best informants and allies in operations at times.
[*] [b]The Siddhe Kingdom[/b]: A conglomeration of the wild spirits of Celtic, German, and French folklore and mythology. They are adept at their own nature-based technology and experts in the alchemical field, infamous for being more unpredictable and traitorous than their more out-and-out demon cousins of the Infernal Empire. The Kingdom is, too, divided into several factions that rule fiefdoms in the realm and claim different hours of the day on Earth to strike. Some, like the Apostles of Samhain, are almost ghost-like in their powers like boggarts, banshees, dullahans and nucklelavees. Others, like the Tuatha de Danaan, are out and out gods who oversee the actions and do political and diplomatic damage control for their less controlled neighbors. The majority, though, are tied to the seasons and many to the elements.
[*] [b]Demigods Unlimited[/b]: An enemy organization to the Infernal Intervention Team but with a similar means, Demigods Unlimited is a for-hire band of mercenaries who are also tied to demons and gods, primarily Greco-Roman or Norse Gods. They work with the more unsavory factions, human and god and demon alike, doing their bidding if something needs doing under the table with no fingers pointed. Their current leaders are Jason, X'balanque, and Gilgamesh, who separately run three outfits of the organization and are all classified as highly dangerous adversaries.
[*] [b]The Shadow Loa[/b]: A group of god-like spirits who are guilty of a few crimes, including child sacrifice, possession, and necromancy. While the majority of Rada Loa of Haitian and African Vodun are allied with the pantheons that support the Infernal Intervention team. They are a major supplier of cults and if not for their more playful, independent insanity and devil-may-care stance on their actions, they would rank far higher on the most wanted list. The most infamous members are: The Ghede Family, led by Papa Ghede; the Baron family, led by Baron Samedi and Maman Brigitte; and the Troublemakers, led by Erzulie Dantu.
[*] [b]Sovereign Nation of the Damned[/b]: Some souls cannot be cleansed and recycled as easily as you can expect. Some of the biggest monsters and mass murderers in history return time and time again, and many of the warlords are household names. Led usually by whichever of the highest ranking three (Vlad Tepes III, Tomas de Torquemada, and Countess Elizabeth Bathory) is the oldest, they have become immortal living viruses that the technology of any one pantheon cannot detain. Most of them have been imprinted by the technology that they were tested as fuel for, and all of them are dangerous and reincarnate at a tremendous rate. Those touched by them have a good chance of ending up becoming one of them.
[*] [b]Children of Gaia[/b]: More elemental and emotional embodiments than anything, these former footnotes of Greek folklore are very much alive and their operations have moved entirely to Earth. Their forces include dryads, naiads, and several orders of monster in addition to having several subgroups, each controlling one element. They are led by the husband-and-wife team of Typhon and Echidna, and are responsible for several natural disasters that they demand ransom to stop. Do not underestimate them.
[*] [b]The New Generation[/b]: The weak coalition of the newest inclusions to the pantheons and whose grip on the Earth used to be the smallest. A manipulation of memetic effects brought about by a tearing of the veil made these creatures, who modern folklore and horror are often based from, become a higher order of being, and often prey on the young and impressionable. They are organized by a former Slavic god, Chernabog, who intentionally put on a new moniker as Bogeyman in order to rally the assembled forces into a military force.
[*] [b]The Knights Templar and the Knights Teutonic[/b]: Two orders of knights that used their knowledge of the Veil hundreds of years ago to set up a minor foothold. The Knights Templar and Knights Teutonic based their works off of the teachings of the "Enlightener", who now claims the spot of one of the Ten Infernos as Baphomet, and the methods of capturing souls and spiritual beings utilized by the old Israeli king Solomon. They are an order of summoners who can implant spirits into anything they choose and enchant technology to enhance its power, and as a military force they have to be kept in check by the combined forces of the Other Side.
[*] [b]The Order of Nine Angles[/b]: A more recent attempt to create a foothold in the world by the very same Inferno Baphomet, the Order of Nine Angles is a mix of some of the worst stigma surrounding Satanic practices. Manipulation, sacrificial magic, thaumaturgy, necromancy and psychomantic hexes are regular mainstays, and their power does not derive from the demon orders, but from an even deeper, darker force that seeks power on a cosmic level as opposed to claiming human souls. There is little known about them but their power is intense and their face popularity is growing by the day.
[*] [b]The Bookmakers[/b]: Probably one of the most ingenious and powerful of the human factions that the Infernal Intervention team may face are the Bookmakers. These people were authors, storytellers who primarily wrote horror or cosmic horror fiction. When the rift was opened, one author with severe mental health issues learned how to harness the power, and then that power spread through his own word of mouth to an online forum he was a part of. The Bookmakers were then formed, who could write and change reality or create their own puppet gods with their words. The site had since been shut down and the group had gone into hiding, but the leaders have not been disbanded or destroyed.
[*] [b]Tulpa Corporation[/b]: One of two corporations profiting off of human potential. Their phrase, "mind over matter", is being utilized through their technology that uses the same mechanics as the Bookmakers but sells it for a profit. They are guilty of multiple human rights violations and have enough sway in third world countries that they can cull the entire populations to use as test subjects, usually selecting the most traumatized or neurodiverse of the population to be part of their Tulpa Project, which allows thoughts to become a sort of false dream-like reality through affecting peoples' perceptions and brainwaves. With literally more money than God and a backing from a percentage of the population who do not want pantheon interference in human affairs and wish to have their own power over their souls, they are more tackled on an individual situation involving test subjects running amok than any steps being taken to truly demolish their endeavors.
[*] [b]Elysium Enterprises[/b]: An unscrupulous company whose goals are far loftier than the Tulpa Corporation, whose motives are entirely for profit. Elysium has plans towards creating a new universe with their technology, whose spiritual power is as useful to Earth and the Other Side as any human soul, and then underselling to the pantheons for a profit. They have no qualms with draining the power of gods and completely obliterating human souls to do this, and they have their sights set on the items and sources of power that could give them enough energy to accomplish their lofty goals at the cost of the balance of power.
[*] [b]The Servitor's Republic[/b]: A country of dark magic users and monsters living together seems like a safe haven for those who wish to be separate from the overall world. But like many non-magical communes, they hold a darker secret, and it's said that anyone who joins the Republic may never again leave.
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There are way more factions and each one can be gone into in more depth, but this is really all you need as a basis point and it's really a list of all the major players as far as the setting is at the beginning. Not all gods from certain pantheons (Greek, Egyptian, Norse, etc) have to hail from these factions, and you don't have to feel obligated to be a member of any one faction outside of the II Team. You can absolutely descend from independent operators or be a lone wizard, but for those who want more direct ties to the world around them, this is a good starting point.