Blightrot

In the end, the Blight came.

Blightrot Cysts during the Storm

Overview

Blightrot is sometimes described as a tax on Rainwater usage. Blightrot generates Blightrot Cysts and these Cysts generate Corruption with continued Rainwater usage. The more water you use in Rain Engines, the more Blightrot 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 Corruption you can spare until 3 random villagers die. You can also hold the SHIFT key and click on the icon to stop all Engines.

Blight Post, Blightfighters and Purging Fire

A Blight Post

A Blightfighter burning a Blightrot Cyst

On the left is a Blight Post, an essential building used to produce  Purging Fire which Blightfighters (villagers assigned to the Blight Post) then use to burn Blightrot 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 Blight Post without upgrades can handle a maximum of approximately 20-25 Blightrot Cysts per Storm Season on Veteran to Prestige 10 Difficulties (this number goes down to around 15 at Prestige 11 and above). Beyond this point, Blight Post upgrades or additional Blight Posts will be needed.

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: Blightfighters and Blight Automatons in this Blight Post need 5 fewer seconds to burn a Blightrot Cyst.
• Mobile Sparkcasters: Blightfighters 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.

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.
• 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.

The Hydrant

A Hydrant

The exact number of Cysts a Blight Post can handle varies depending on the movement speed of your Blightfighters, and also by Cyst location – the less time your Blightfighters 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 Blight Post and the infested buildings is too great.

When assigned to a Blight Post, Harpies have a +10% chance to double their  Purging Fire production, and Lizards get +5 to their Resolve.

Blightrot Cysts and Removal

During the Storm, Blightfighters can burn Blightrot Cysts with  Purging Fire produced in Blight Posts. Each Cyst burned removes 50 Corruption. A Blightfighter will burn a Cyst for approximately 15 seconds before it disappears.

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 to  Purging Fire. Any Cysts left close immediately as soon as the year ticks over and Drizzle Season starts, even if they were in the process of being burned.

Corruption

Corruption bar in the Ancient Hearth

Blightrot infects Hearths. The more Blightrot Cysts a Viceroy generates from Rain Engine use or Glade Events, the faster their Hearths get corrupted during Storm Season, when Blightrot Cysts open up. Once the Ancient Hearth reaches the Corruption limit, it triggers Voice of the Sealed Ones. Voice of the Sealed Ones sends out 3 ghosts from the Ancient Hearth that seek out and kill 3 random villagers. As soon as the [earth discharges, Corruption is reset to 0 and starts rising again.

Lowering Corruption

The only reliable way to lower Corruption during Storm is to employ the help of Blightfighters in a Blight Post. Every Cyst burned lowers Corruption by 50. Once all Cysts have been burned, any new ones will not open up till next Storm Season. Any Cysts left close immediately and Corruption resets to 0 as soon as the year ticks over and Drizzle Season starts.

You could also remove Cysts by destroying all of the buildings that have Cyst slots. Most buildings you construct have them. With only the Main Warehouse left, you will have no more than 6 Blightrot Cyst slots.

Corruption Resistance and Corruption rate

Corruption Resistance or Hearth Resistance is a measure of how high the Corruption limit is. The higher the Corruption Resistance, the more time it will take for Voice of the Sealed Ones to activate. An Ancient Hearth that hasn't been upgraded has 1000 Corruption Resistance. Every Ancient and Small Hearth level raises Corruption Resistance by 150. It can also be raised with different effects.

The Corruption rate per Cyst is 60 Corruption/minute up to Prestige 10, and 90 Corruption/minute from Prestige 11 onwards.

Assuming a Hearth upgraded to level 2, you will reach the Corruption limit of 1300 at least once without burning any Cysts:

• At 60 Corruption/minute in a 2-minute Storm with 11 Cysts.
• At 60 Corruption/minute in a 4-minute Storm with 6 Cysts.
• At 90 Corruption/minute in a 4-minute Storm with 4 Cysts.

Forest Mysteries influencing Corruption

Mystery	Penalty	Activation
Unyielding Corruption	Favoring unavailable if Hearth is Corrupted.	Hostility 3
Leakage	-300 Hearth Resistance.	Hostility 2

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.

Perks and Cornerstones influencing Blightrot

Blightrot Perks and Cornerstones

Name	Rarity	Description	Sources
			Alt	Cor	Ord	Rel
Baptism of Fire	Legendary	Every 3 burnt Blightrot Cysts lowers Hostility by 10. While the Hearth is corrupted, you’re unable to sacrifice resources.	x	Cor	x	x
Blight Filter	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.	x	Cor	x	x
Blightrot Pruner	Legendary	Blightrot spores aren't technically eggs, but they taste the same. You gain 5 Eggs when a Blightrot Cyst appears in your settlement.	x	Cor	x	x
Burnt to a Crisp	Legendary	Gain 20 Coal for every 3 burned Blightrot Cysts.	x	Cor	x	Rel
Overexploitation	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 a Blightrot Cyst.	x	Cor	x	x

Corruption Perks and Cornerstones

Name	Rarity	Description	Sources
			Alt	Cor	Ord
Alarm Bells	Legendary	The Brass Order's newest invention. All workers have a +5% higher chance of producing double yields for every 90 points of expected Corruption per minute in the Ancient Hearth.	x	Cor	x
Alarm Bells (Stormforged)	Mythic	The Brass Order's newest invention. All workers have a +33% higher chance of producing double yields for every 100% points of expected Corruption per minute in the Ancient Hearth.	Alt	x	x
Ancient Stabilizer	None	The Ancient Hearth's resistance to corruption is increased by 100.	x	x	Ord
Firekeeper's Armor	Epic	Allows firekeepers to combat corruption more efficiently. Every burned cyst removes an additional 50 corruption.	x	Cor	x
Forbidden Seal Shard (Stormforged)	Mythic	It was not you who removed this fragment, weakening the ancient seal - but you would still be executed on the spot if someone was to find it in your possession. Every Glade Event solved by making a decision marked as Corruption increases the chance of workers producing double yields by +5%. (the bonus is added retroactively)	Alt	x	x
From the Shadows	Legendary	Confused, empty-eyed creatures emerge from the Hearth. Each time Voice of the Sealed Ones triggers after the Hearth reaches 100% Corruption, 3 new villagers appear in the settlement.	x	Cor	x
Obsidian Runestone	Epic	A complicated runic structure, designed to shield the hearth from corruption. The Ancient Hearth's resistance to corruption is increased by 400.	x	Cor	x

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!