Debuff

Debuff is a gameplay element in Fire Emblem Heroes that reduces a character's stats under certain conditions.

Types of Debuffs
A debuff is caused by certain skills which can be divided into two types based on their activation criterias: Field Debuff and Combat Debuff.

Field Debuffs
Field Debuffs are visible stat changes highlighted in red. They are usually activated at start of a turn or after a unit's combat. These debuffs do not stack together, only the highest value will be applied to an affected stat. They do, however, stack with Field Buffs.

{|width="100%" class="mw-collapsible"
 * colspan=2|List of skills with Field Debuff effect:
 * -valign=top

Weapons

 * Argent Bow
 * Aversa's Night
 * Barb Shuriken
 * Bottled Juice
 * Clarisse's Bow
 * Cloud Maiougi
 * Dancer's Fan
 * Dark Breath
 * Deathly Dagger
 * Dusk Uchiwa
 * Eckesachs
 * Fear
 * Felicia's Plate
 * Fensalir
 * Forblaze
 * Geishun
 * Goodie Boot
 * Grima's Truth
 * Hikami
 * Hliðskjálf
 * Hoarfrost Knife
 * Huginn's Egg
 * Iron Dagger
 * Ífingr
 * Kabura Ya
 * Kagami Mochi
 * Kitty Paddle
 * Kumade
 * Lethal Carrot
 * Lyfjaberg
 * Muninn's Egg
 * Ouch Pouch
 * Pegasus Carrot
 * Peshkatz
 * Poison Dagger
 * Red-Hot Ducks
 * Reese's Tome
 * Rogue Dagger
 * Sabertooth Fang
 * Seashell
 * Silver Dagger
 * Sky Maiougi
 * Slow
 * Smoke Dagger
 * Starfish
 * Steel Dagger
 * Sylgr
 * Sæhrímnir
 * The Cleaner
 * Valflame
 * Wagasa
 * Wargod's Tome
 * Weirding Tome
 * Wind's Brand

Passives

 * Attack Feint
 * Attack Ploy
 * Attack Smoke
 * Chaos Named
 * Chill Attack
 * Chill Defense
 * Chill Resistance
 * Chill Speed
 * Chilling Seal
 * Defense Feint
 * Defense Ploy
 * Defense Smoke
 * Freezing Seal
 * Resistance Feint
 * Resistance Ploy
 * Resistance Smoke
 * Sabotage Attack
 * Sabotage Resistance
 * Seal Attack
 * Seal Attack Defense
 * Seal Attack Speed
 * Seal Defense
 * Seal Defense Resistance
 * Seal Resistance
 * Seal Speed Defense
 * Seal Speed
 * Speed Feint
 * Speed Ploy
 * Speed Smoke
 * Threaten Attack
 * Threaten Defense
 * Threaten Resistance
 * Threaten Speed
 * }

Combat Debuffs
Unlike Field Debuffs, Combat Debuffs are not visible but they instead can be observed in the Combat forecast to evaluate the outcome of the battle. They are only activated during combat. These debuffs stack together with no upper limit, along with Field Debuffs and Field Buffs if any.

{|width="100%" class="mw-collapsible"
 * List of skills with Combat Debuff effect:

Weapons

 * Adult (Cavalry)
 * Book of Dreams
 * Book of Shadows
 * Brazen Cat Fang
 * Covert Cat Fang
 * Eldhrímnir
 * Foxkit Fang
 * Kitsune Fang
 * Loptous
 * Sæhrímnir
 * Taguel Fang
 * Tharja's Hex
 * Whelp (Cavalry)
 * Yearling (Cavalry)
 * }