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 in Rain Engines, the more Blight Cysts and Corruption you 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. You can also hold in the SHIFT key and click on the icon to stop all Engines.

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

Blight Post, 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. A Blightfighter will burn a Cysts for approximately 15 seconds before it disappears. Every Cyst removed lowers Corruption by 50 points.

Blight Post Upgrades

Blight Posts can be upgraded up to two times:

LEVEL I (Choose 1)
Cost:
2  Pack of Building Materials + 4  Pipes

• Triple Ignition System: Blight Fighters and Blight Automatons in this Blight Post need 5 fewer seconds to burn a Blightrot Cyst.
• Alchemical Forge: +50%  Purging Fire double production chance in this Blight Post.
• Blight Automaton: assigns a Blight Automaton that helps burn Blightrot Cysts to this Blight Post. They can't produce  Purging Fire and don't take up worker slots.

LEVEL II (Choose 1)
Cost:
2  Pack of Building Materials + 6  Pipes

• Manned Lookout: the use of water in Rain Engines generates Blightrot Cysts 10% slower for every worker assigned to this Blight Post.
• Mobile Sparkcasters: Blight Fighters assigned to this Blight Post move 30% faster.
• Blight Automaton: assigns a Blight Automaton that helps burn Blightrot Cysts to this Blight Post. They can't produce  Purging Fire and don't take up worker slots.

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 Blight Posts) will burn Blightrot Cysts with  Purging Fire produced in Blight Posts. 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 third Clearance Season, 5* 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.

*before Prestige 11.

Forest Mysteries and Blightrot

Mystery	Penalty	Activation
Natural Filtration	Using Rain Engines causes a lot less Blightrot contamination due to the natural filtration processes of the surrounding vegetation. Blightrot Cysts grow 50% slower when using Rain Engines.	Drizzle
Absorption	Burning Cysts takes 5 seconds longer.	Hostility 2
Blight from the Sky	Every Storm Season, 1* Blightrot Cysts appear in the settlement (multiplied by the number of years that have passed).	Hostility 4
Blightrot Infection	When a villager leaves or dies, 2* Blightrot Cysts will appear in the settlement.	Hostility 3
Rotten Vapors	Pay 5  Drizzle Water x number of years, or 3* Blightrot Cysts will spawn.	Hostility 3
Spreading Contamination	+5% faster Queen's Impatience gain for every Blightrot Cyst in your settlement.	Hostility 4

*before Prestige 11.

Glade Events and Blightrot

Effect	Event	Type	Explanation
Engine Corrosion	Blightrot Cauldron	Event Consequence	Contaminated liquid gets inside Rain Engines through underground pipes. Using water in Rain Engines generates Blightrot Cysts 50% quicker.
Growth Medium	Rainpunk Cauldron	Working Effect	The Blightrot inside the Rainpunk Cauldron feeds on everything it encounters. For every 20 food produced, 2* Blightrot Cysts are spawned in the settlement.
Voice of the Forest	Withered Tree	Working Effect	Trees communicate with each other through their roots, making the forest aware of your every move. Spawns 1* Blightrot Cysts every 120 seconds for every 2 Dangerous or Forbidden Glades discovered.
Effective Parasite	Withered Tree	Event Consequence	The Blightrot feeds on the tree's valuable nutrients, making new cysts much more resilient. Cysts burn for 5 seconds longer.
Friend or Foe	Corrupted Caravan	Working Effect	The forest is merciless to those who exploit it. To protect itself, it may even sometimes ally with the Blightrot. Every 120 seconds, 1* Blightrot Cysts are spawned for each earned Hostility level.
Straight to the Hearth	Corrupted Caravan	Event Consequence	Your settlement's strongest and weakest point has become a direct target for the Blightrot. Corruption in the Ancient Hearth grows 50% quicker.
Blight Incantation	Altar of Decay	Working Effect	A powerful, necrotic curse. Burning Blightrot Cysts takes 10 more seconds. Hostility is increased by 45** points for every  Wildfire Essence stored in the settlement's Warehouse.
The Night's Embrace	Altar of Decay	Event Consequence	The settlement is slowly engulfed in darkness. Each Blightrot Cyst increases Hostility by 15** points during the storm.
Awakening	Infected Drainage Mole	Working Effect	Upon awakening the Infected Mole, all dormant Cysts activate and start to Corrupt the Ancient Hearth. Cysts are vulnerable to  Purging Fire when this effect is activated. Completing or canceling the Event will not stop the Corruption, and Cysts will remain active until burned.
Infestation	Infected Drainage Mole	Working Effect	Blightrot becomes extremely aggressive. 8* Blightrot Cysts will spawn in the settlement. Each cyst increases Hostility by 30** points.
Overflow	Noxious Machinery	Working Effect	The machine is somehow connected with the settlement's underground pipe system. You lose 4 units of a random type of Rainwater every 12 seconds. Every 120 seconds, 2* Blightrot Cysts are spawned in the settlement.
Blightrot Outbreak	Noxious Machinery	Event Consequence	The explosion of the machine will not only destroy everything within a 10** field radius, but will also cause 5* Blightrot Cysts to spawn in the settlement.

*before Prestige 11.
**value on Viceroy Difficulty and higher.

Cornerstones and Blightrot

Effect	Source	Description	Explanation
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.
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.
Blightrot Pruner	Cornerstone Legendary	Blightrot spores aren't technically eggs, but they taste the same.	You gain 5  Eggs when a Blightrot Cyst appears in your settlement.
Burnt to a Crisp	Cornerstone Legendary	—	Gain 20  Coal for every 3 burned Blightrot Cysts.
Overexploitation	Cornerstone Legendary	—	Global gathering speed is increased by 30%, and newly discovered resource nodes have more charges (+10 charges to small deposits, +25 charges to large deposits). Every depleted resource node spawns 1* Blightrot Cyst.
Firekeeper's Armor	Cornerstone Epic	Allows firekeepers to combat Corruption more efficiently.	Every burned Cyst removes an additional 50 Corruption.

*before Prestige 11.
**value on Viceroy Difficulty and higher.

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 100% quicker.

References

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