The Picts (Galam Cennalath)
Start Bias: Hill
UA: Masters Of Fortriu
Units gain a +33% Combat Bonus against more advanced units. Cities started on Hill Tiles gain additional City Defensiveness and do increased damage when bombarding enemy units.
UB: Crannog (replaces Garden)
+25% Great Person generation. Requires a source of Fresh Water. Tiles with access to Fresh Water generate +1 Culture.
UB: Broch (replaces Castle)
+7 City Defensiveness, +25 HP. Enemy units that end their turn within one hex of the City sustain 30 points of damage every turn. Generates +4 Production if a Great General is garrisoned in the City.
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Dál Riata (Aedan mac Gabrain)
Start Bias: Coastal
UA: Three Kindreds
Occupied Coastal Cities stay in Resistance for half the usual time. Gain additional Faith from Trade Routes to Civilizations with whom you have a Declaration of Friendship.
UU: Currach (replaces Trireme)
Weaker and faster than the Trireme it replaces. May also perform Trade Missions.
UI: Insular Cross (all new!)
Unlocked at Masonry. +1 Faith. Additional +1 Faith and +2 Culture after Archaeology is researched, and generates another +1 Faith if the City working it contains a Monastery. If Pillaged, gain 50 Faith.
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Sudreyjar (Godred Crovan) [Hebrides]
Start Bias: Coastal
UA: Plurimarum Insularum
Gain -2 Unhappiness and +1 Culture in the Capital for each Atoll tile in the Empire. Naval Units gain a +5% Combat Bonus when attacking for each 25 Tourism the Empire produces.
UI: Bothy (all new!)
Unlocked at Construction. +25% Combat Bonus for any Unit occupying the tile, and generates +2 Food and +1 Production whenever so occupied. Counts as a Farm for technology-related bonuses (Civil Service and Fertilizer).
UU: Crofter (replaces Settler)
After it is used to found a City, a Worker appears in it.
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Strathclyde (Rhydderch Hael)
Start Bias: Grassland
UA: Dyrnwyn Aflame
May purchase any unlocked pre-Gunpowder unit with Faith. Doing so generates Culture. Land Units gain a +25% Combat Bonus when attacking.
UU: Novantae (replaces Swordsman)
Gain extra health from Pillaging tiles. Start with Cover I.
UU: Rheged Band (replaces Pikeman)
May be purchased with Gold for half the usual price. Does additional damage to Cities as well as Mounted units.
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Northumbria has already been made! Which is awesome and wonderful and thank you for giving me mod credit on it. =]
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Kent (Aethelberht)
Start Bias: Coastal
UA: Invicta
Land Units gain a +10% Combat Bonus while defending, with an additional +5% bonus for each Kentish Great Work in the Capital.
UU: Bretwalda (replaces Great General)
Standard Great General bonuses. In addition, may be spent to generate Tourism while at war with the target Civilization, or create a Great Work of Writing.
UI: Oast House (All new!)
Can only be built on flat land with access to Fresh Water. +1 Food and +1 Culture. The Culture yield rises to +2 after Architecture is discovered, and +3 after Biology is discovered. Unlocked at Engineering.
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Wessex (Alfred)
Start Bias: Grassland
UA: Burghal Hidage
Defensive Buildings grant a flat Gold boost when built. Defensive Buildings in the Capital also give a free copy of a Unique Unit from any Civilization not in the game for which you possess the required Technology. Units garrisoned on Forts generate -1 Unhappiness.
UU: Shieldwall (replaces Swordsman)
Slower than the Swordsman it replaces, but starts with Cover I. Gains an additional 1% Combat Bonus for every Unit it kills from a major Civilization or City-State.
UB: Court Of Scholars (replaces University)
+33% Science generation bonus. +2 Science per worked Jungle Tile. 2 Scientist Specialist Slots. +1 Production, +1 Gold, +1 Culture. Contains a slot for a Great Work of Art. Substantially more expensive to produce than the University it replaces, and cannot be bought with Gold. May not be built in conquered Cities.
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Mercia (Offa)
Start Bias: Grassland
UA: Greatest Of Seven
Trade Routes with City-States generate +1 Influence over that City-State per turn and grant a +5% Culture Boost to the City that initiated the trade. International Trade Routes generate Culture per turn.
UB: Sceattas Maker (replaces Mint)
+2 Gold per Gold or Silver Resource worked by the City. Also provides a +10% Gold generation bonus across the Empire.
UB: Jewelmaker (replaces Workshop)
+2 and +10% Production. 1 Engineer Specialist Slot. Creates one copy of the Jewellery Luxury Resource. Also contains a slot for a Great Work of Art, which grants a +1% bonus to Culture generation per 2 base Production in the City when filled.
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(Wales is part of the Celtic Civilizations split, and these guys are contemporaneous to the others, so...)
Gwynedd (Rhodri I)
Start Bias: Hill
UA: Y Hen Ogledd
Gain a +33% boost to Research towards a technology if a Civilisation you have met has already discovered it. Great Writers may construct Academies.
UB: Limewashed Church (replaces Temple)
+2 Faith. Contains one slot for a Great Work of Writing. +1 Science after Architecture is discovered.
UU: Gruffydite (replaces Spearman)
Gains an additional +10% Combat Bonus for each Terrain Type in a one-hex range around the tile where it ends its turn. Generates Science per kill.
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Deheubarth (Hywel Dda)
Start Bias: Plains
UA: The Laws Of The Good
-1 Unhappiness from Specialists. Specialists generate +1 of their primary yield in Cities with a Constabulary and a further +2 in Cities with a Police Station.
UU: Milwr Gosod (replaces Knight)
Weaker and slower than the Knight it replaces, but may attack twice, with the second attack dealing 75% damage. Costs slightly more.
UB: Caer Dinefwr (replaces Castle)
+7 Defensiveness, +25 HP. Increases City Bombardment Range to three hexes and causes it to deal additional damage against Siege Units. Costs considerably more than the Castle it replaces.
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Normandy (William I)
Start Bias: Grassland
UA: First Crusaders
Mounted Units start with Shock I, do additional damage against Units from Civilizations that follow a different majority religion, and generate Faith per turn when garrisoned in a City. The Production costs of Land Units are increased by 33%.
UU: Milites (replaces Knight)
Substantially stronger than the Knight it replaces, but more expensive to build and cannot be bought with Gold. May be purchased with Faith.
UB: Opus Gallicum (replaces Castle)
+15 City Defensiveness, +38 HP. The City in which it is built generates Faith when its bombardment kills an enemy unit.
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Connacht (Tairrdelbach Ua Conchobair)
Start Bias: Coastal
UA: Tribes Of Galway
+1 Global Happiness per International Sea Trade Route. Tiles that generate Gold may be purchased for free.
UU: Connaught Ranger (replaces Musketman)
Starts with a unique Promotion, "The Devil's Own", that grants a major bonus when attacking but a substantial penalty when defending. Gain a flat amount of Gold when used to capture Cities.
UB: Dun Ro Caislean (replaces, you guessed it, Castle. It's almost like they're everywhere in Britain and Ireland...)
+7 Defensiveness, +25 HP. The City now counts as a source of Fresh Water. +25% Gold bonus from International Trade Routes to and from this City.
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Leinster (Ugaine Mor)
Start Bias: Hills
UA: Province Of The Spear
Land Units gain a +5% Combat Bonus for each Tile with Iron worked in the Empire. Mounted Units receive Terrain Bonuses.
UU: Laigin (replaces Spearman)
Additional Combat Strength. Does extra damage against more technologically advanced units, which is retained upon upgrading. May embark across Ocean tiles.
UU: Redbreast (replaces Lancer) (Yes I know they were first raised in Enniskillen the synergy's better so deal with it)
Start with Formation I & II, along with a unique Promotion, "Quis Separabit", that allows them to deal 33% extra damage to Melee units. Costs significantly more than the Lancer it replaces. Upgrades to Cavalry.
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Ulster (Fiachnae mac Aedo Roin)
Start Bias: Grassland
UA: Annals Of Ulster
Theming Bonuses generate +2 Faith per turn. Buildings that generate Faith also generate +1 additional Culture.
UU: Ulaid Archer (replaces Composite Bowman)
Weaker and more expensive than the Composite Bowman it replaces, but has +1 Range. Also starts with the unique promotion "Cattle-Raiders of Cooley", which means it counts as a Great Work of Writing when garrisoned in a City.
UB: Abbey (replaces Shrine)
+2 Faith. +1 Faith for every other Faith-generating Building in the City.
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Munster (Cormac mac Cuillenain)
Start Bias: Plains
UA: Sanas Cormaic
A Great Prophet is born in the Capital after researching Writing and founding a Pantheon. 50% of the points generated towards a Great General or Great Admiral go towards Great Scientists
UB: Leabharlann (replaces Library)
+1 Science per 2 Citizens in the City. Contains a slot for a Great Work of Writing that comes pre-filled. When filled, generates +1 Faith per 2 Citizens in the City.
UU: Geraldine (replaces Longswordsman)
Slower than the Longswordsman it replaces and cannot be used to capture Cities. However, gains a permanent +5% Combat Bonus for each City or City-State you Liberate (once per City) and has a very high Combat Strength (27 compared to 21). Upgrades directly to Rifleman and obsoletes at Rifling.