Magic contamination

Version 0.34: This article is up to date for the latest stable release of Dungeon Crawl Stone Soup.

Magic contamination is a dangerous condition caused by miscasts and some magical effects.

Overview

Various activities cause harmful magical energies to accumulate in your body. A small amount of magical contamination (a grey "% Contam" status) is harmless and will dissipate over time without any further effect. Larger amounts of accumulated magic contamination (a yellow or red "Contam" status) will make you start to Glow with magical contamination. Contamination is reported as a percent out of 300% maximum, internally tracked as 0-3000 points of contamination.

Being at a severe contamination level makes you easier to hit and reveals you if Invisible, similar to the Corona spell. It also lowers stealth and puts you at risk of Bad mutations and damaging explosions. The chance of exploding scales with contamination severity. Damage scales with player XL. Explosions at 200%+ contamination have increased radius and damage. When this happens, a mutation check will occur with a 1 in 5 chance of a single bad mutation or random Mutation (this is heavily weighted toward bad mutation outcomes).

Any amount of contamination can cause Ugly things adjacent to you to change their colour.

Contamination Levels

Contam	Colour	Description
0-999 (0-99%)	Grey	You are very lightly contaminated with residual magic.
1000-1999 (100-199%)	Yellow	You are dangerously contaminated with residual magic. (Explosions up to 27 damage at XL 27)
2000-2999 (200-299%)	Red	You are extremely contaminated with residual magic. (Explosions up to 33 damage at XL 27)
3000 (300%)	Red (Max)	You are completely saturated with residual magic! (Explosions up to 33 damage at XL 27)

Sources

Spells

• Irradiate: 185-400 per cast.
  • When a player is hit by Irradiate: 400-600.

Spell Miscasts

• Every Miscast: Depends on the miscast severity. See Miscast effect for more information.

Other

• Removing an Artefact with *Contam: 1200
• Removing a weapon with Distortion brand: 3000 (25% chance)
• Removing the Plutonium Sword: 700-1350
• Mutagenic fog: 250-500 per turn
• Zot trap: 1500 - 3000 (one of many possible outcomes)
• Jiyva Penance: 0 - 100 * penance (one of many possible outcomes)

Dissipation

Magic contamination begins to dissipate after 7 turns at the rate of 20 per turn. Quaffing a Potion of cancellation instantly removes -1 * (250-1000) points of contamination.

Tips & Tricks

Being undead or in lichform, by way of Talisman of death, prevents any contamination-related malmutations; instead, you are temporarily drained.

Amulet of dissipation will increase the rate at which contamination is resolved, thus reducing the number of bad outcomes.

Summary of Major Changes in 0.34 Compared to Prior Versions

For clarity, these Dev notes summarize the major changes detailed specifically above and should allow players to adjust their expectations from the old system:

• Contam has been rescaled internally. 1000 is now the start of yellow, 2000 the start of red, and 3000 the absolute cap.
• Contam decays faster, but does not start to decay until 7 turns have passed since contam was last gained.
• Low yellow is somewhat more dangerous than before and the difference between low/high has been narrowed. Very high levels of contam are worse than before (the mid-range is similar to the prior state).
• Being invisible no longer prevents all contam decay.
• Evoking a scarf of invisibility no longer gives a tiny bit of contam (it was largely irrelevant, requiring 6 consecutive uses to hit yellow).
• Contam explosions are possible at lower levels of contam than before, do significantly more damage (and ignore the player's AC), are non-elemental, and their base damage is based on the player's XL rather than the amount of contam. Yellow-tier explosions are radius 1, red are radius 2 and do more damage than yellow.
• Contam mutations no longer have a 50% chance to ignore rMut (along with a few other narrow interactions with mutation conflicts due to counting as 'forced'). This seems unnecessary, with rMut being both weaker and far rarer than when this system was first designed.
• Contam is now listed as a percentage on the UI, while contaminated (near the Doom indicator). Yellow is 100% (ie: the start of actual negative gameplay effects), red is 200%, and the cap is 300%. While the specific number is admittedly unimportant for minor contam, it helps make the difference between low/high transparent to the player, and critically, allows contamination-costing spells to be more transparent about what their risks are in the current moment.
• Contam is only shown on the status line once you have enough for it to have gameplay impact (ie: yellow or worse).

History

• In 0.34, a major rework of contamination system to clarify and simplify. All contam-inflicting things have been adjusted. The average number of mutations gained "should remain similar" to the old version. GitHub ref
• Prior to 0.29, the contamination level for the light grey warning was 3500 instead of 3000. This change was enacted to match Irradiate, which had its contamination increased in this version.
• Prior to 0.28, the Orb of Zot extended contamination.
• Prior to 0.26, magic contamination decayed much slower: -25 per turn instead of -75, while the time between bad effects was also slower (200 - 600 turns).
• Prior to 0.25, miscast effects were different, and thus had different contamination levels.
• Prior to 0.19, the light grey contamination level didn't exist.
• Prior to 0.10, this effect was simply called glow, a ambiguous term that also referred to the backlight caused by Sticky Flame and Corona (and contamination itself).

Sources of Contamination

• Prior to 0.28, invisibility caused contamination over time, and Disjunction had 750 - 1250 contamination on cast.
• Prior to 0.26, casting Controlled Blink or reading a scroll of blinking contaminated the player.
• Prior to 0.20, drinking a potion of haste contaminated the player, and the haste effect caused contamination over time.