Debuff
A 
debuff is a status effect that can be inflicted on either monsters or heroes to lower one or more of their stats or resistances. The presence of a debuff is indicated by a double downward orange arrow under the affected target. The opposite of debuffs are buffs.
List of debuffing Heroes
TBA
Applying debuffs
A debuff is usually applied through an ability, though traps can also inflict them upon heroes when being triggered or when disarming fails. Some abilities, for example many of the Hellion's attacks, can debuff the user as well. When an ability or trap carrying a debuff effect hits a hero or enemy, a random check will determine if the target will be affected, taking its debuff resistance into account. All abilities inflicting debuffs will have a 100% chance of inflicting them before calculating the appropriate resistance value.
Removing and preventing debuffs
A hero affected by a debuff can get rid of it by using Cleansing Salt or Ginseng Powder. It is also possible to prevent debuffs from being applied by raising the hero's resistance to them, typically with the use of trinkets or, as a temporary means, through the use of Alum Censers. Debuffs inflicted by curios can generally be prevented by using the correct supply item when cleansing them.
Duration and stacking of debuffs
The same debuff can be stacked indefinitely with itself on the same target, multiplying its effects for the duration. Typically, as per most status effects, each individual stack of a debuff will last for three turns, however there are exceptions such as debuffs inflicted by traps, which will typically last 12 turns, and curios, which can have varying durations up to "until camp".
Debuff Resist
All heroes have a base resistance to debuffs, which affects how likely they are to be debuffed by enemies. Hero skills with a self-debuff attached to it (such as Finale) do not take Debuff Resist to the account. Like most other hero resistances, Debuff Resist increases by 10% per Resolve Level.
The list of heroes by their base Debuff Resist, from highest to lowest:
