Blightrot

In the end, the Blight came.

Blight Cysts during the Storm

Overview

Blightrot is sometimes described as a tax on Rainwater usage. Blightrot generates Blight Cysts and these cysts generate Hearth Corruption with continued Rainwater usage. The more water you use, the more Blight Cysts and Corruption generate. You can view your Hearth Corruption percentage on the bottom right of your screen. Clicking on the Icon will take you to the Hearth Corruption information page, where you can view how many Blightrot Cysts have generated as well as how much Blightrot generation you can spare until 3 random Villagers die.

From Veteran to Prestige 10 difficulty, the rate of Corruption generation is 60% Corruption a minute per Blightrot Cyst. It multiplies by 1.5x starting from Prestige 11.

Blightpost, Blightfighters and Purging Fire

A Blightpost

A Blightfighter burning a Blight Cyst

On the left is a Blightpost, an essential Building used to produce Purging Fire which Blightfighters (Villagers assigned to the Blightpost) then use to burn off Blight Cysts during the Storm Season. Viceroys can also build a Hydrant to store extra Purging Fire near buildings that have grown a lot of Cysts. Purging Fire is made by using Coal , Sea Marrow, Oil or Wood.

A single Blightpost can handle a maximum of approximately 20-25 Blightrot Cysts per Storm Season on Veteran to Prestige 10 difficulty (this number goes down to around 15 at Prestige 11 and above). Beyond this point, multiple Blightposts will be needed.

The Hydrant

A Hydrant

The exact number of cysts a Blightpost can handle varies depending on the movement speed and Global Work Speed of your Blight Fighters, and also by cyst location – the less time your Blight Fighters spend walking between the Blight Post and the cysts, the more cysts they will be able to burn. A well-placed Hydrant will greatly reduce this travel time, and may be essential if the distance between your Blightpost and the infested buildings is too great.

Harpies in a Blightpost have a +10% chance to double their Purging Fire production, and Lizards in a Blightpost get +5 to their Resolve.

Blightrot Cysts and Removal

Blightfighters (Villagers assigned to the Blightpost)) will burn Blightrot Cysts with Purging Fire produced in the Blightpost. This will remove Corruption.

A closed Blightrot Cyst

An open Blightrot Cyst

On the left is a closed Blightrot Cyst, cysts will remain closed during Drizzle Season and Clearance Season, and they are invulnerable during this time. On the right is an open Blightrot Cyst, cysts will open during the Storm Season, and they are now vulnerable and able to be burned off with Purging Fire by Blightfighters.

Difficulty Modifiers influencing Blightrot

Difficulty Modifier	Description	Explanation
Prestige 3	Large swathes of Blightrot migrates accross the realm.	Every 3rd Clearance Season, X amount of Blightrot Cysts will spawn.
Prestige 11	The Blightrot's impact is stronger.	Blightrot Cyst generation rate is now increased by 100%, the Hearth corrupts +50% quicker than normal and all effects that spawn Blightrot now add twice as many Cysts.

Forest Mysteries and Blightrot

Forest Mystery	Description	Explanation
Natural Filtration	Using Rain Engines causes a lot less Blightrot contamination due to the natural filtration processes of the surrounding vegetation.	Blightrot Cysts grow X% slower when using Rain Engines.
Rotten Vapors	Machinery has to be cleaned with specially prepared Drizzle Water. Otherwise, Blightrot will spread.	Once this effect activates, you have to pay X amount of Drizzle Water (multiplied by the number of years). If you don't, 3 Blightrot Cysts will spawn in your settlement.
Rot from the Sky	The rain smells like Blightrot...	Global food production is slowed by X for each Hostility level.
Spreading Contamination	Blightrot contaminates everything you send to the Citadel.	During the storm, the Queen's Impatience grows X faster for every Blightrot Cyst in your settlement.
Blightrot Infection	Villagers report feeling sick, especially during the storm.	When a villager leaves or dies, X Blightrot Cysts will appear in the settlement.
Absorption	Blightrot Cysts consume the storm's energy and become more resilient.	Burning cysts takes X seconds longer.
Blight from the Sky	Blightrot seems to grow uncontrollably quickly in this region.	Every storm season, X Blightrot Cysts appear in the settlement (multiplied by the number of years that have passed).

Glade Events and Blightrot

Glade Event Effect	Event	Explanation
Growth Medium	Rainpunk Cauldron	The Blightrot inside the Rainpunk Cauldron feeds on everything it encounters. For every X food produced, X Blightrot Cysts are spawned in the settlement.
Voice of the Forest	Withered Tree	Trees communicate with each other through their roots, making the forest aware of your every move. Spawns X Blightrot Cysts every X seconds for every X Dangerous Glade discovered.
Friend or Foe	Corrupted Caravan	The forest is merciless to those who exploit it. To protect itself, it may even sometimes ally with the Blightrot. Every X seconds, Blightrot Cysts X are spawned for each earned Hostility level.
Blight Incantation	Forsaken Altar	A powerful, necrotic curse. Burning Blightrot Cysts takes X more seconds. Hostility is increased by X points for every Wildfire Essence stored in the settlement's Warehouse.
Infestation	Infected Drainage Mole	Blightrot becomes extremely aggressive. X Blightrot Cysts will spawn in the settlement. Each cyst increases Hostility by X points.
Overflow	Noxious Machinery	The machine is somehow connected with the settlement's underground pipe system. X. Every X seconds, X Blightrot Cysts are spawned in the settlement.

Perks, Cornerstones and Blightrot

	Source	Description	Explanation
Amber for Water	Cornerstone Legendary	Apparently, there is a technique for extracting crystals similar to Amber from rainwater.	Gain 10 Amber every time you use 50 units of water in Rain Engines. Blightrot Cysts grow 25% quicker when using Rain Engines.
Blight Filter	Cornerstone Legendary	A crystalline filter designed to mitigate the negative environmental impact of infused rainwater..	Blightrot Cysts appear 50% slower when using rain engines, but Reputation from Resolve is generated 90% slower for the next 2 Reputation Points.
Burnt to a Crisp	Cornerstone Legendary		Gain 20 Coal for every 3 burned Blightrot Cysts.
Baptism of Fire	Cornerstone Legendary		Every 3 burnt Blightrot Cysts lowers Hostility by ‑10. While the Hearth is corrupted, you’re unable to sacrifice resources.
Effective Parasite	Event Consequence	Withered Tree	The Blightrot feeds on the tree's valuable nutrients, making new cysts much more resilient. Cysts burn for X seconds longer.
The Night's Embrace	Event Consequence	Altar of Decay	The settlement is slowly engulfed in darkness. Each Blightrot Cyst increases Hostility by X points during the storm.
Engine Corrosion	Event Consequence	Blightrot Cauldron	Contaminated liquid gets inside Rain Engines through underground pipes. Using water in Rain Engines generates Blightrot Cysts X quicker.
Straight to the Hearth	Event Consequence	Corrupted Caravan	Your settlement's strongest and weakest point has become a direct target for the Blightrot. Corruption in the Ancient Hearth grows X quicker.
Blightrot Outbreak	Event Consequence	Noxious Machinery	The explosion of the machine will not only destroy everything within a X field radius, but will also cause X Blightrot Cysts to spawn in the settlement.

Plagues and Blightrot

Plague	Description	Explanation
Plague of Corrupted Water	The rainwater has become contaminated, so rainpunk machinery is now even more hazardous.	Using rainwater in rain engines generates Blightrot cysts X quicker.

References

Thanks to Discord users Jhazrun, Aphant and Benedict for supplying much needed information to complete this page!