Acid Rain

*"A toxic downpour falls over the wasteland seas!"*

The **Acid Rain** is a weather event added by the Calamity Mod that occurs in the Sulphurous Sea biome. It has a 1/360,000 chance of occurring every frame (1/6000 every second) once the Acidsighter has been defeated, or can be summoned manually through the use of a Caustic Tear.

The event has multiple levels of difficulty that are encountered at different stages in progression similar to the Old One's Army, with each tier unlocking after the player has defeated a specific boss. The first tier of the event will be unlocked after the Acidsighter has been defeated, the next tier will unlock after the Aquatic Scourge has been defeated and the final tier will unlock after the Polterghast has been defeated. Each tier features the introduction of new enemies as well as buffs and new behaviors to existing enemies.

## Content

Nuclear Toad
Radiator
Skyfin
Water Leech
**If Aquatic Scourge has been defeated:**

Flak Crab
Irradiated Slime
Orthocera
Sulphurous Skater
Trilobite
Cragmaw Mire(Miniboss)
**If Polterghast has been defeated:**

Gamma Slime
Mauler(Miniboss)
Nuclear Terror(Miniboss) | **From Acid Eels, Nuclear Toads, Radiators, and Skyfins:**
Sulphuric Scale
**From Nuclear Toads:**

Caustic Croaker Staff
**From Water Leeches:**

Parasitic Scepter
**From Radiators caught with a Bug Net:**

Radiating Crystal
**From Flak Crabs, Orthoceras,  Sulphurous Skaters, and Trilobites:**

Corroded Fossil
**From Flak Crabs:**

Flak Toxicannon
**From Flak Crabs after defeating the Polterghast:**

Cadaverous Carrion
**From Orthoceras:**

Orthocera Shell
**From Orthoceras after defeating the Polterghast:**

Insidious Impaler
**From Sulphurous Skaters:**

Sulphurous Grabber | **From Acid Eels after defeating the Aquatic Scourge:**
Slithering Eels
**From Acid Eels after defeating the Polterghast:**

Vitriolic Viper
**From Skyfins after defeating the Aquatic Scourge:**

Skyfin Bombers
**From Trilobites after defeating the Polterghast:**

Toxicant Twister
**From Irradiated Slimes and Gamma Slimes:**

Lead Core
**From Cragmaw Mire:**

Spent Fuel Container
Nuclear Rod
Nucleate Gello
**From Cragmaw Mire after defeating the Polterghast:**

Septic Skewer
**From Maulers:**

Shark Fin
Sulphuric Acid Cannon
Fetid Emesis
Prehistoric Tablet
**From Nuclear Terrors:**

Sulfuric Scale
Gamma Heart
Phosphorescent Gauntlet
Microxodonta | **If Polterghast has not been defeated:**
Music Box (Acidic Downpour)
**If Polterghast has been defeated:**

## Event Progress

Unlike other weather events, the Acid Rain has a progress bar and can be completed. To complete the event, the player must gain 90 points in the first tier, 115 in the second, and 140 in the third. In Multiplayer, the number of points required is calculated by the expression `(amount in singleplayer) * ln(total players + e - 1))`, rounded down, based on how many players are in the world at the start of the event.

If the player doesn't kill any enemies within the time span of four minutes, the event will automatically cancel and progress is reset for the event. The event can also be prematurely ended with a Torrential Tear or the non-consumable variant of the Caustic Tear.

The following is a list of enemies in the Acid Rain event and the amount of points gained from each enemy per kill. Minibosses are marked in **bold**.

## Aftermath

### Any Tier

* The Sea King will begin selling Caustic Tears.
* Abyssal Crates will contain Sulphuric Scales.

### Tier 2 or 3

* Abyssal Crates will contain Corroded Fossils, Belching Saxophone, Flak Toxicannon, Nuclear Rod, Skyfin Bombers, Slithering Eels, Spent Fuel Container, and Sulphurous Grabber.

## Notes

* While the Acid Rain event is active, Rain will be active across the rest of the world.
* The event's enemies will override the Sulphurous Sea's enemies, similarly to Meteor Heads.
* Other weather events such as the Blood Moon can overlap with the Acid Rain event.
* After the player has defeated the Acidsighter, the Acid Rain is guaranteed to begin the next time they visit the Sulphurous Sea. This only occurs once.
* If the Acidsighter has never been defeated, the event still becomes available once Hardmode begins.

## Tips

* This event is very dangerous for early game players due to the high spawnrates of enemies.
* Due to the event only occurring on the far side of the world, it's highly recommended the player sets a spawn close to the Sulphurous Sea in order to save time in the case that they die.

## Trivia

* The Acid Rain's theme is **corrosion!**, which was composed by wiki editor RoverdriveX.
	+ Its music box is titled "Acidic Downpour".
	+ If the Calamity Music add-on mod is disabled, the Old One's Army's theme will play instead.
* The final tier's theme is **nuclear monsoon**, which was composed by PinpinNeon
	+ Its music box is titled "Sulphuric Monsoon".
	+ If the Calamity Music add-on mod is disabled, the Solar Eclipse's theme will play instead.
	+ This theme is a remake of the final tier's previous theme, **radioactive**, which was also composed by PinpinNeon.
* It is the second event added to the Calamity Mod, following the Boss Rush.
* Some of the event's enemies are based on extinct aquatic lifeforms, such as the Orthocera and Trilobite.
* Several designs of the event's enemies are also based on artworks submitted for a Sulphurous Sea enemy design contest on the Calamity Mod's art discord server.
* The event used to be a variation of the Rain event in the Sulphurous Sea, similar to Blizzards in the Snow biome.
	+ Prior to that, it was known as "Irradiated Rain" and replaced Rain after the Moon Lord was defeated.