Clouds are lingering area-of-effect ("AOE") effects. New to Dominions 6, they can get thicker with repeated applications, though they still thin out over time. Multiple kinds of clouds can be in the same square (with one exception), but only 7 "cloud levels" can fit in one.

Clouds thin out at roughly a rate of 1 cloud level per battlefield round. Older clouds dissipate first.

Clouds of the same type generally don't actually overlap; if they do, it increases the existing cloud by 1 level at most (instead of being treated as its own thing), and the new clouds displace the old ones otherwise. In other words, a level 1 cloud effect can only create level 2 clouds at most, through affecting the same place twice in a tight-enough window.

Everything from a Cloud is Armor-Negating. Some clouds are nonmagical, however, so the Ethereal will only rarely have to breathe them in.

The point-value effects of clouds, Damage (DMG) and Fatigue (FAT), were applied strangely in Dominions 5. To account for units moving through cloudy squares, points were divided by 3, rounded up, and doled out roughly every sixth of a round. It is not yet clear if that is still the math; many other things were changed about clouds, such as clouds of the same type now combining into higher-level clouds instead of overlapping.

The kinds of clouds and their effects are hard-coded and tied to their level. This is a departure from previous games, which also had a different list of cloud spells and considered some of these effects to be "auras".

Also known as Fire Clouds, these are most-commonly spread by the Heat trait on certain units. Regardless of the point value of this trait (which merely indicates how many clouds it spawns in a combat round), it lays clouds of only 1 level.

The cloud deals (level)+1 Fire Fatigue, and (level)-2 Fire Damage. Only Fire Clouds of level 3 or higher deal damage.

Also known as Chill Clouds or Freezing Mists, these are most-commonly spread by the Chill trait on certain units. Regardless of the point value of this trait (which merely indicates how many clouds it spawns in a combat round), it lays clouds of only 1 level.

The cloud deals (level)+1 Cold Fatigue, and (level)-2 Cold Damage. Only Freezing Mists of level 3 or higher deal damage. The damage is capped (unable to be higher than 1 after Damage/Protection DRNs) unless the target is frozen.

Frost Clouds and Heat Clouds are the only clouds that cannot coexist in a single square; their levels cancel each other out.

These foul clouds are most-commonly spread by certain units with the Poison Cloud trait, which only lays clouds of 1 level like the above two. This sort of cloud can be nonmagical, in which case the Ethereal (breathing in another dimension) are mostly safe.

The cloud deals Poison Damage equal to its level.

Spread by Sulphur Haze, Sulphur Clouds have a mixed effect.

The cloud deals (level)/2 Fire Fatigue, and (level)/2 Poison Damage. The Fatigue is rounded up, while the Poison Damage is rounded down. The Poison Damage is capped, with higher levels merely helping the DRN and knocking Poison Resistance.

Spread by the Cloud of Death spell, Death Clouds deal Magic Damage equal to their level. This is resisted by a Death Magic Resistance check with a Penetration of 11.

Spread by the Leeching Darkness spell, a Leeching Cloud primarily applies 1 point of Weakness to those inside; this is a minor Affliction, a lesser version of the standard "Weakness" that reduces Strength by 1 (per point).

Its actual effect (or at least the strength of the effect) depends on the cloud level.

Level	Effect
1	1 Weakness (7 Penetration, Death)
2	1 Weakness (7 Penetration, Death), 1 Capped Magic DMG (7 Penetration, Death)
3	1 Weakness (11 Penetration, Death), 1 Capped Magic DMG (7 Penetration, Death)
4+	1 Weakness (11 Penetration, Death), 1 Capped Magic DMG (11 Penetration, Death)

A "Shimmering Light Cloud" is pretty rare, but it deals "false damage". The power scales as follows:

Level	Effect
1	1 Capped False Magic DMG (7 Penetration, Glamour)
2	1 Capped False Magic DMG (11 Penetration, Glamour)
n	n-1 False Magic DMG (11 Penetration, Glamour)

Primarly spread by Plague Carriers such as a Mummy, the Disease Cloud inflicts Disease on those passing through who fail a Death Magic Resistance check. For level 1 and level 2 clouds, the Penetration is 7. For level 3 or higher clouds, the Penetration is 11.

Also known as a Cloud of Dreamless Slumber, these clouds are not particularly common. Those who succumb to it fall asleep; resisting requires a Glamour Magic Resistance check, with a Penetration of 7 for level 1 clouds and a Penetration of 11 for higher levels.

Spread by the Rust Mist spell, Rust Clouds rust the gear of those who pass through; weapons, armor, and even the odd iron shield.

These aren't in Dominions 6. They were in Dominions 5, though, so they may return in a later update.