Plagues: A simplified idea for a Game Mode


Jun 8, 2019
I no longer think it's feasible to expect a complex system of pandemics/plagues in either NFP or afterwards.

With that said I have a simplified idea for a Pandemic game mode which uses already existing game assets and mostly copies already existing code.

Note: The purpose here is not to achieve realism, but rather a way to enhance some game elements, such as Tile Appeal, which is unfortunately too often irrelevant in the game.

Pandemic Game Mode:

The mode would require Gathering Storm.

is a peculiar type of natural disaster which spreads similarly to forest fires, but rather than woods or rainforest, in order to spread it requires an adjacent marsh, district or improvement, including roads. It pillages all tiles it spreads to and damages any unit it hits.

1.1 When spreading to a district, it only damages the highest tier building currently intact. It's essentially a one-off "Pillage" action.
E.g. A tile with both an improvement and road will only pillage the improvement. A tile with only a road will pillage the road.

1.2 When a plague spreads to a Harbour or Airport, there's a chance of it spreading to other Harbours or Airports within 6-9 tiles.

1.3 Plagues typically last 4 turns. After a plague subsides in a tile, that tile is immune from plague for four turns.

1.4 Tiles with Plague do not provide terrain yields for the duration of the plague.

The chance of a Plague occurring and spreading depends on the Tile Appeal of any tile with a marsh or improvement/district. The lower the appeal, the higher the chance of a plague initiating there.

2.1 A tile requires at least -1 Appeal for a new Plague to initiate there, but may spread to any other legal tile.

2.2 Plagues cannot spread to tiles with Breathtaking Appeal.

2.3 When using the Apocalypse Mode, Soothsayers can be used by the player to initiate plagues in any legal tile.

2.4 Existing Governor promotions:
a) Liang's Reinforced Materials promotion blocks any chance of plagues spreading to tiles in the city.
b) Reyna +1 Appeal from Forestry Management is also an indirect buff to this governor in this mode.

Other than pillaging the tile, Population loss may occur. The extent of damage depends on Natural Disaster Intensity.

3.1 Whenever a Marsh is hit by a plague, the tile gains +1 Science. Maintaining isolated Marshes for scientific purposes rather than farming them becomes a viable approach.

Two new units from the Black Death Scenario are made available, the Flagellant and the Plague Doctor (though with different mechanics):

a) The Flagellant is a unique melee military unit with Combat Strength set by the current Era and with a unique promotion tree. It has higher base Combat Strength in tiles afflicted by Plague and is immune to Plague Damage.
Some possible promotions include:
- Higher Movement in Plague tiles;
- Stealth in Plague tiles;
- Heals in Plague tiles;
- May attack twice, etc.

b) The Plague Doctor is a support unit also immune to plague damage which comes with 3 charges. These may be triggered to reduce the length of Plague in a tile by two turns and doing so provides a lump sum of Culture and Science, set by Era. It may enter neutral territory without open borders agreements. Using a Plague Doctor in foreign territory provides Diplomatic Favor points on top of Science and Culture.

4.1 A new Dark Age policy which makes all of your traders immune to it and which provides +1 Science and +1 Culture in the Capital for every plagued tile within your empire.

Duke William of Normandy

King of England & Unofficial Welcoming Committee
Jul 27, 2020
Rouen, Normandy
So basically the Black Death Scenarios in Civ 6 except more nuanced? Hell yeah!! :)

Also, that Dark Age Policy is good, but it needs some counter-balance, as do all the other Dark Age Policies.
Oct 17, 2017
I like the idea of plagues only spreading to lower appeal tiles and have never thought of that before. I guess it makes since that diseases might be found more prevalent in "lower income" places specifically thinking lower appeal neighborhoods, at least I think that's the idea trying to be conveyed.

Considering it would require Gathering Storm I would also like to propose a Pandemic Emergency for the World Congress.
Civs with a research lab building could initiate Discover a Cure project for points.
You also have the option of maybe sending gold to civs ravaged by a pandemic or send plague doctors to them.

Also maybe the sewer or the medic should help in the game mode somehow. Maybe the sewer could give "appeal" to tiles in the city in the game mode. :mischief:
Of course maybe at least a hospital building could work better in the game mode which could even go in the Neighborhood and function the same as the sewer would.


Jun 8, 2019
Considering it would require Gathering Storm I would also like to propose a Pandemic Emergency for the World Congress.

I initially wrote an Emergency but then removed it as I felt it was maybe complicating it too much, replacing it with the "Plague Doctors gain Diplo Favor when used on foreign tiles".

But I'm not opposed to the idea.

The thing that bothers me the most in my OP is the pillaging though. Repairing tiles is no fun. So perhaps rather than pillaging improvements and roads, plagues just make those tiles temporarily unusable, forcing the player to rely on less efficient tiles for the duration. Plus the AI is notoriously trash at fixing stuff.

The high tier building in a district could still get pillaged since it doesn't involve workers.

Mr. Salt

Aug 23, 2020
Of course, it would be unreasonable not to stipulate some changes to fundamental game elements. Here are my ideas:
Sanitation tech: Plagues have 2 turns shorter duration empire-wide.
Sewer improvement: -50% chance of a Plague starting in any tile in this city.
All Roads Lead to Rome: -50% chance of a Plague starting in any Roman tile when Construction is unlocked. The Sewer does not stack with this.
New building: Hospital: Unlocked by Sanitation. Built in the Neighborhood. -3 turns of Plague duration in this and adjacent tiles. Plague Doctors trained in this city have an additional charge.
Victor, the Castellan: Tier 1 "Garrison Commander" promotion replaced by new "Quarantine Enforcer" promotion: -2 turns of Plague on tiles in this city. His quick reassignment makes this promotion ideal if you see a cloud of Plague working its way down a Trade Route toward your city.
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