Faction Effects

Skaven -

Clan Eshin:
Hero Recruit Rank +3 for Assassins (Faction Wide)
Melee Attack +5 for Night/Gutter/Death Runners (Faction Wide)
+2 Ranks for Night/Gutter/Death Runner Recruits (Faction Wide)

Clan Moulder:
+10 Armour for Rat Ogres/Hellpit Abominations - Moulder are the makers of the monsters, saving the best for themselves
+10% Weapon Damage Rat Ogres/Hellpit Abominations
+1 Chaos Corruption (Faction Wide) - What exactly does go on in those pits?

Clan Skryre
+2 Skaven Corruption (Faction Wide) - Intentionally mostly negative faction trait - The Skryre factories make things a mess
Hero Recruit Rank +2 for Warlock Engineers (Faction Wide)
+10% Missile Damage Warpfire Throwers/Globadiers/Bombadiers/Warp Lightning Cannons/Doomwheels (Faction Wide) - Skryre are the best at making skaven tech
+5% Research Rate

Clan Spittel
+5 Melee attack for clanrats/stormvermin against Lizardmen - They hunt the Lizardmen
+10 armour for clanrats and stormvermin - they use the lizardmens skin to make better armour

Clan Mordkin
Stormvermin cause Fear - Many Chieftains and Stormvermin of Clan Mordkin wear a helmet made from the skull of a Giant Rat or even a Rat Ogre, sounds sort of spoopy.
+5 leadership against undead (VC and tomb kings when they come out) - They're used to fighting the undead.

Clan Gnaw
+10 melee attack -5 melee defence for clanrats and storm vermin - barbaric in nature, their foot infantry might be more offensive in nature, that and I thought it interesting (if it's possible)
+25% income from Hunting Camps/Lairs/Tanneries - they're proficient hunters

Dark Elves -

Ghrond
+3 Ranks for Sorceress - Tons of sorcery
+5 Leadership for all male troops (Faction Wide) - They utilise sorcery and seduction to ensure loyalty
+5% Upkeep (All troops faction wide) - Decadent
Resistance to Chaos Corruption maybe

Hag Graef
Loyalty -2 for new recruits - Lots of infighting
+3 Ranks for Khainite Assassins - Many assassins dwell here
+15% income from buildings - Extremely wealthy city
+2 chevrons for cold one cavalry - they're the OG cold one knights

Karond Kar
+15% Slave income - Dark Elf Slaving capital
+2 Ranks Corsairs/Corsairs Hand Bows - Main port of the Dark Elves
+5 Leadership at sea
-15 Diplomatic relations with High Elves/Bretonnians/Imperials - They enslave people of these nations primarily

Clar Karond
-15% upkeep/cost for harpies and hydras - they have the best beastmasters among all the Druchii
Frenzy for harpies - best beastmasters again + they primarily worship Anath Raema and are very savage.

The Forgebound
+5% missile damage/reload speed with artillery - My head canon is they're focused on engineering and foundries
+5 armour for all melee infantry - Again with previous head canon + their starting iron mines, they are perhaps experienced smelters
+10% income from mining
-2 Public order - due to squalor from the mines and foundries

Blood Hall Coven
-20 Diplomatic Relations with the Cult of Pleasure - They ran away from Morathi in lore
+10% chance of sorceress success on campaign map - They were 3 sorceress's who ran off from Morathi, so sorceress theme here.
+3 ranks for sorceress

Bleak Holds
+2 ranks for shades - They're along the mountains where the Shades make their home
+10% reload speed for shades
-15% recruitment/upkeep shades

Cult of Excess
+20 diplomatic relations with High Elves - Infiltrators?
-5 leadership for enemy High Elves

Deadwood Sentinels
+10% campaign map vision - they're sentinels and scouty, or something
+10% Speed for Dark Riders
-15% Upkeep for dark riders

Scourge of Khaine
Frenzy for Corsairs (Lord's army) - crazed pirate invaders? maybe?
+5 melee attack against High Elves

SS'ildra Tor
+5 melee attack against Lizardmen - The SS'ildra Tor have no lore, but perhaps as the closest faction to the Lizardmen they have some experience fighting them.
-20 diplomatic relations with Morathi - Seeing the spread of Chaos from Morathi's cult they are none too fond of her.


High Elves -

Avelorn
+2 Public Order - Everybody loves the Everqueen, and the court of Avelorn tends to be incredibly happy
+2 Influence per turn - She's also the second most influential person in Ulthuan behind the Phoenix King
+10 Diplomatic Relations with all other High Elves

Caledor
-15% Upkeep and Recruitment for Dragons - Dragon tamers
+5% Weapon Damage for all Elven units (Faction Wide) - Vauls anvil where they forge the greatest of Elven weaponry lies in Caledor.
-5 Diplomatic Relations with everyone - Particularly arrogant even for elves

Chrace
+25% Chance to successfully ambush - Master ambushers in the wooded lands of Chrace
-15% Upkeep and recruitment cost for White Lions of Chrace
+5 melee attack in home region - They defend Chrace like mad

Cothique
+20% Income from ports - They're a sea faring region and the only High Elves who are very interested in nations other than Ulthuan.
+10 Melee attack at sea - They're the best mariners

Ellyrion
+2 Ranks to all cavalry units - They're the horsemasters of the High Elves
+5% Speed/+5 Charge Bonus for all cavalry (Faction Wide) - Zippy elves

Nagarythe
+8 Leadership against Dark Elves (Faction Wide) - They hate them, a LOT.
-40 Diplomatic Relations with Dark Elves - I mean, they REALLY ♥♥♥♥♥♥♥ hate them.
+10% chance of agent success - And they sometimes use sabatoge to deal with them.

Tiranoc
-10% upkeep/recruitment cost for chariots - they're the OG chariot lords
+3 Melee attack for all units (Faction Wide) - They're the most warlike of all the High Elf nations, always being the first to answer the call to war from the Phoenix King.

Yvresse
-5 Growth - It's a dying land
Immune to sea attrition - They have increidbly hard to navigate waters, so perhaps they got used to such things.
+5% Reload reduction/damage for archers - they do have some notable archers
+10 range to archers - is this even possible? If not +5% more reload/damage.

Chaos -

Sarthorael the Ever-Watcher
+5% Ward Save (Faction Wide) - Tzeentch on TT were all about the ward save
+10 Winds of Magic (Faction Wide) - Tzeentch also about dat magic.

Greenskins -

Black Venom
All Goblins have poison (Lord's Army)
15% missile damage/reload for forest goblin spider riders

Bloody Spearz
+2 Ranks for all Night Goblins (Faction Wide)
-20% Upkeep for all Night Goblin units - They're a night Goblin Clan

Broken Nose
+10% reload rate for Goblin Rock Lobber (Faction Wide) - This clan stole dwarven Siege weaponry, and perhaps in the process learned a little about artillery.
+10 armor for goblin units - Maybe they stole some armor while they were at the Dwarven armories?
+10% upkeep for orc units - Orcs gotta be well compensated to follow some little gobbos around

Scabby Eye
+10 charge/5 melee attack for goblin cavalry - They're a goblin wolf riding tribe
+15% raiding income - I imagine wolf riders would be pretty efficient about getting around raiding.

Skullsmasherz
+5% weapon damage for orc units - they got big smashy weapons
-30% upkeep for trolls - they have their pet trolls to help smash some skulls in

Teef Snatchaz
+20% income from post battle loot - snatching some teef
+5% speed for all units - gotta be zippy fast to get in there and steal some teef

Araknos
-20% upkeep/recruitment for Arachnarok Spiders
+10 leadership in subterranean battles
+2 ranks for Night Goblin Shamans

Lizardmen -

Itza
+5 Leadership/5 Melee Defence in Home regions (Faction Wide) - Protectors of the greatest temple city still standing
+25 Diplomatic relations with other Lizardmen - Other lizardmen would not be prone to risking damage to the great city of Itza.

Tlaxtlan
+15% Campaign view distance - City of astrology, there's other lore stuff that has this make sense too but I'm too lazy to get into it.
+3 ranks for Skink priests

Xlanhuapec
+15% Research rate - City of ancient artifacts, the tech would help advancement.
+15% missile damage/reload rate for Solar Engines - more tech

Sentinels of Xeti
-20% cost/upkeep for Chameleon Skinks/Terradon Riders
+10% missile damage for Chameleon Skinks/Terradon Riders

Teotiqua
-50% attrition from undead land
+2 to untainted (Faction Wide)
-20 diplo with Undead - I dunno, they're near undead and I can't think of ♥♥♥♥ so I went with this, hadn't done the untainted thing before either.

Wood Elves-

Bowmen of Oreon
+10% Campaign Movement - very helpful for a pack of nomadic wood elves, and elves are zippy fast.
+2 ranks for all archer units - they're some lethal bowmen.

Wydrioth
Frenzy for army when under siege - They're vicious in their defence of the woods
-10% recruitment/upkeep for waywatchers - As a faction fanatic in their defense of Athel Loren they'd likely want waywatchers to defend the paths into the woods.

Dwarfs-

Barak Varr
+10% Trade tariffs - Notable trade with both other dwarfs as well as humans.
+10 melee defence at sea - Barak Varr is known for it's very well crafted iron vessels
+10 relations with humans - they're quite friendly with most humans compared to other dwarves and trade with them and even aid in foreign wars (to ensure their shipping lanes keep open)

Karak Norn
-15% upkeep for irondrakes/flame cannons - They like to have fire weapons ready at hand in case they are needed against the Wood Elves whom they strongly distrust
+5% missile damage for irondrakes/flame cannons
+5 melee defence when under siege - they have very strong defences in the mountains.
-10 relations with Wood Elves - They do not very much like them

Zhufbar
+5 armor to all units - well known for their forges and as a great source of precious metals used in the smithing of their strong armours.
+3 ranks to engineers - primary shrine for the engineering guild located here
+2 Max Engineers

Karak Hirn
Units cause fear when under siege - I wanted to somehow reflect the Hornhold here, and this was the best I could come up with, not sure if it's even possible.
+10 leadership for longbeards - I just went with what you had put as a starting unit, perhaps their longbeards are particularly stubborn and grumbly.
-10% recruitment for longbeards

Karak Ziflin
+5 melee attack/defence for Ironbreakers
+3 ranks for thanes

Greybeard Prospectors
Miners +10 armor +5% weapon damage - better equipped miners to deal with local hostiles
Mining buildings cost 10% less and make 10% more money - I dont even know if this is possible

Karak Dank
Rangers have strider and 10% movement increase (Faction Wide) - Being in the jungle for so many years their rangers might have learned quite a bit about moving about
+3 ranks to rangers - also because my head canon has rangers as their primary military force in the jungle (that heavy armor would be cumbersome in the humid jungle swamps) they have more experienced ones on hand

Vampire Counts-

Necrarch Brotherhood
Increased Replenishment by 15% - their expertise in necromancy allows them to bring back the dead more swiftly
-20% upkeep for corpse carts and black coaches

Strygos Empire
+5 ranks for Strigoi ghoul kings
+10 armor for crypt ghouls and crypt horrors

Silver Host
+15 diplomacy with everyone - Lahmian infiltration
+5 ranks for vampire heroes - Lahmians are a pretty powerful bloodline of all females, the vampire heroes are all female.

Vampire Coast
-20% upkeep recruitment/cost for zombies - always a corpse on hand washed up upon the shore
+5 leadership at sea - pirate zombies arrr
+10% campaign movement while at sea - if possible (dont think it is)

Norsca-

Aesling
+5 leadership for all marauders - they're bloodthirsty and don't afraid of anything
+3 speed for marauders - and they want to get in their fast to chop ♥♥♥♥ up
-20 diplomatic relations with Baersonling - Long time rivals

Baersonling
-20 diplomatic relations with Aesling - Long time rivals
+20% income from razing/looting - barbaric ♥♥♥♥♥♥♥♥
Their Fimir cause terror instead of fear - Because reasons
-20% upkeep for fimir

Bjornling
Marauder Berserkers have Frenzy (Lords Army) - They go ham, key word is Berserkers so thought they should be super specialty there
Marauder Berserkers cause Fear (Faction Wide)
Shamans cost 10% more - they don't got no time for silly magic

Graeling
+10% weapon damage for skinwolves and werekin - their skinwolves are stronk and savage
-15% upkeep/recruitment for skinwolves
-10% upkeep from buildings - but theyre savages, so they're not very good at that economic mumbo jumbo

Skaeling
+5 ranks for shamans - they're wily, using that mystical mumbo jumbo.
+5 leadership at sea - they worship Mermedus who's sort of like a sea god of sorts
-10% upkeep for frost wyrms

Varg
-15% upkeep and recruitment for chariots - chariot spam memes
+15 charge for all chariots (Lord's Army) - Surtha Ek's charioteers are no joke, apparently.

Bretonnian Crusaders-

Knights of Origo
All knights have frenzy (Lords army) - going by their rather ancient TT roles
-10% to all income - they need a huge weakness for such a massive strength, and apparently even though they were on a trade line they just sort of spent their time meditating and weren't interested in actually trading or worrying about the economy.

Knights of the Flame
All of their Knights have burning attacks - Is this even possible? I think poison is anyway
-50% losses from undead attrition - think their name fits an undead crusade name, so I sort of went with it, their is plenty of undead relatively near to them too.

Thegan's Errantry
+15% trade tariffs - They've got the cape of the Southlands and the Knights of Origo are not interested in trade, so presumably a lot would go through here.
-2 Public Order - the locals hate them
-35% upkeep for Royal Hippogryph Knights

Skeggi
+5 melee attack at sea - wish there could be something more interesting for naval factions
-15% cost and upkeep for Marauder champions - It's a place where many great norscans have gone to find glory and riches.

Mung
-30% upkeep for Norscan warhounds - well when you starve your dogs they don't cost much to keep around
+10% campaign movement range - nomadic

Aghol
+10 charge bonus for cavalry - Kurgan horse people
+20% income from post battle loot
+10% weapon damage for cavalry units - They're very strong people, rumored to be either mutated or super human.

Beastmen-

Manblight Tribe
-50% from all attrition - Other than the ungrol four horns stuff not much is known about them, but living out in the red desert in game maybe they're a pretty tough lot?
+10 leadership for gors and bestigors -5 leadership for ungors - they bully the poor ungors, maybe more than some other beastmen, but it's gotta feel good for those up the food chain
+5 melee attack against humans - wouldn't be too relevant most of the time so not really neccessary, but thought it fit the name

Blooded-Axe Tribe
+10% weapon damage for great weapon units - their big old axes are very stronk
+2 bestial rage - not sure if even possible

Ripper-Horn Tribe
+10% campaign movement
+20 charge for razorgor herds and chariots

Shadowgor Tribe
+2 Chaos Corruption (Local Province)
Cygors and Giants have a 10% phsyical resist

Other-

Erengrad
+15% income from ports - The port of Erengrad gives them experience at sea trade
-20 Diplomatic Relations with Kislev, Ostland and Kraka Drak - The rebellion makes them quite unfriendly with Kislev and those friendliest with her
+10% reload speed/missile damage for outriders and pistoliers - the Ungols make the finest skirmishers, (all these suggestions from Vern on discord)