To better understand the numbers, here's an example:
"Conquest +"modded value" ("original value", "how much I increased it")".


Huns:
Conquest +50 (+25, x2) growth from razing settlements
War: +2 (+1, x2) integrity for every war being prosecuted
Famine: +40 (+20, x2) food consumption in provinces where the horde is present
Death: stops replenishment and about everything else where the horde is present.

White huns:
Income +200% (+100%, x2) from sacking, looting and raiding
War: +2 (+1, x2) integrity for every war being prosecuted
Attrition: Immune to desert attrition (all armies)
Morale: +40(+20, x2) versus eastern empires ***


Eastern Roman Empire:
Income +15% (+5%, x3) interest on treasury at the end of turn
Trade tariffs: +100% (50%, x2)

Western Roman Empire:
(removed) Upkeep cost: -4% (-2%, x2) per non-Roman unit in a military force)
(New) Legacy of Mars: Armour: +5% for melee infantry units, +10% for melee sword infantry units and +20% for Herculiani Seniores
(New) Upkeep cost: -40% for non-Roman units recruited from friendly hordes
Constant immigration (+20 (+10, x2) from immigration)
Immigration public order penalties -65% (-50%, x1.3)


Sassanid Empire:
Income +200% (+100%, x2) tribute from puppet states
Puppet state levies +10(+3, x3,3) of each type of levy unit


Suebians:
Horde buildings construction cost: -70% (-35%, x2)
-50% (-35%, x1.3) upkeep for 10 turns for any army that loots or sacks a settlement

Vandals:
(new)Masterwork Cranks: Missile fire rate for all artillery is massively reduced (reload +50)
Can recruit superior quality naval units
Income +200% (+150%, x1.33) from raiding and sacking

Alans:
(New)Thunderous Hooves: Charge bonus: +100% for Shock cavalry
Battle experience gain rate +200% (+100%, x2) for Cavalry units (does this effect even work??)
No post-battle casualties for cavalry units which have router or withdrawn from battle

Ostrogoths:
No instabiltiy when occupying settlements from roman factions (factionwide)
can recruit roman units in settlements with roman military buildings
(new)Upkeep cost: -25% for all Roman units

Visigoths:
(removed as it doesn't work as it says. It's actually a percentage modifier)Food +10 when migrating through roman territory
(New)Food: +100% (+10%, x10) from buildings when migrating through Roman territory
income +1000(+500, x2) from the formation of tributary states
(New)Recruitment cost -50% for levy units


Langobards:
Emancipators: Trippled (doubled, x1.5) unit replenishment when taking on defeated troops post battle
The Fury of Our Make's Hand: +20(+10, x2) unit morale when fighting against armies of other religions.
(New)Research rate: +10% for military developments

Burgundians:
Icy determination: +20% (+10%, x2) unit replenishment
Harsh sustenance: +30(+15, x2) food for every region with poor fertility.

Saxons:
Income +200 (+100, x2) for every 10% damage caused to settlements during a battle
Integrity +8 (+4, x2) when raiding
Raiding stance enables replenishment

Alamans:
Royal splendour +100% (+50%, x2) to general's radius of influence (all characters)
frontiersmen: +30(+15, x2) melee attack versus romans.

Franks:
Integrity -100% (-50%, x2) penalty from casualties suffered
Melee damage +30%(+10%, x3) for every 25% casualties suffered by a unit


Danes:
Immune to seasickness
Immune to high-seas attrition
(New) Recruitment cost: -75% for Naval units

Jutes:
Extra income for every enemy unit destroyed (0,2 to 2, x10)
Income +1000% (+200%, x5) from razing settlements

Geats:
Morale +20 (+10, x2) when fighting during the winter
Immune to snow attrition
(New) Food: +50


Ebdanians:
Sacking and looting income +150%(+75%)
Income +200(+100) for every 10% damage caused to settlements during a battle
(New)Morale +10 when laying siege

Picts:
Enables night battles on land and sea
Morale +18(+9, x2) during night battles (fixed so it actually works)
(New)Melee attack: +18 during night battles (fixed so it actually works)

Caledonians:
Agent action cost -40% (-20%, x2)
Success chance: +50% (+25%, x2)
Agent recruitment cost: -60% (-30%, x2)


Aksum
Supply network +60 (+30, x2) food from each active traderoute (maximum 300 (150, x2)) ***
merchant guards +200% (+100%, x2) to mercenary pool replenishment rate
Commercial mastery +20% (+10%, x2) income from trade

Lakhmids:
Subsided Peace: +1000 (+500, x2) wealth per turn while at peace with the sassanids
Heavenly Cities: +50% (+25%, x2) increased replenishment inside a settlement (all forces)

Tanukhids:
Rapacious Horde: Food Obtained only through settlement battles when Horde (x2)
Victory Rallies: Additional Horde Growth gained through successful battles (x2)
Swelling Ranks. Raiding stance provides free rebellion Militia unit (don't know how to increase)

Himyar:
Fatigue rate: -50% (-15%, x1.33) for all units
Ma'rib Dam: Unique fetility-boosting building at the capital.
Desert Saboteurs: Stops foreign replenishment in regions where armies are present.

Garamantians:
Irrigation: +2(+1, x2) fertility bonus in all provinces
-100% (-50%, x2) conversion time of the main building chain
Morale: +30 (+15, x2) when in own or allied territory


Sclavenians:
Morale, Melee defence, Melee attack: +20 (+10, x2) and Melee damage +40% (+20%, x2) when fighting Nomadic Factions (all forces)
Extra income for every enemy unit destroyed. (1 to 2, x2)
Public order: +10 (+5, x2) from military presence

Anteans:
Morale Melee Defence, Melee attack: +40 (+20, x2) and Melee Damage: +40% (+20%, x2) when fighting in a forest ( all forces)
Morale Melee Defence, Melee attack: -10 and Melee Damage: -10% when fighting on grasslands or open fields ( all forces)
Morale, Melee defence, Melee attack: +40 (+20, x2) and Melee Damage: +40% (+20%, x2) when fighting a river battle (all forces)

Venedians:
Venedi Farms: Farms do not have any negative effects (squalor or public order).
Income +250% (+100%, x2.5) from farms
Income: -50% from commerce, industry & culture