Debuff (XC3)

Debuffs are a mechanic in Xenoblade Chronicles 3. They are temporary detrimental effects applied to characters in combat, marked by a downwards-pointing red pentagon near the character's marker (to the right of it for party members, below it for enemies). The beneficial version of debuffs are s.

Some Stances grant the user detrimental effects. However, they are distinct from debuffs. The key difference is that only one Stance can be in effect on any one character at one time, whereas a character can be under the effect of multiple debuffs.

Using debuffs
Debuffs are typically applied via using offensive s. Doing so applies a particular debuff to the target of the attack. Some Arts apply random debuffs; several debuffs cannot be granted from any of these (e.g. ).

If two party members Interlink, the resulting Ouroboros will have each debuff which was originally on each of the two characters. If the Interlink is cancelled before such a debuff expires, both Interlink members will have the debuff.

Several debuffs can only be inflicted by enemies.

Duration
Each debuff lasts for a standard length of time. However, this can be extended with the right effects. The formula for how long a debuff lasts is: DebuffDuration = BaseDuration * ((1 + sum of DurationBonus) * FusionMultiplier * ShackleRingMultiplier + sum of DurationExtension) In this formula:
 * FusionMultiplier is 2 if the Art used to inflict the debuff was used as part of a Fusion Art and said Art has a Fusion Bonus that increases duration; it is 1 otherwise.
 * ShackleRingMultiplier is the multiplier from the effect of a Chain Ring, Shackle Ring, or Mighty Link on the Art used to inflict the debuff (see the linked pages for details), and 1 if this is not applicable.
 * DurationBonus contains any other effect which increases debuff duration when the debuff is applied, and is zero if no such effects exist. The effects which increase debuff duration are:
 * Sapping Gambit
 * Eternal Curse
 * Refined Incantation
 * Antibody System (negative effect; reduces debuff duration)
 * Debuff Counter (negative effect; reduces debuff duration)
 * DurationExtension contains any effect which increases debuff duration after the debuff has been applied. It updates the remaining duration on the debuff immediately when the effect applies. The only such effect accessible to the party is Mega Crescent.

Each debuff has a maximum duration (in most cases equal to twice its base duration); if the above formula would mean a debuff's duration is greater than its max duration, it is set equal to its max duration instead. This applies to DurationExtension if the effect would cause the debuff's total duration (before and after applying the effect) to exceed the max duration. However, effects that make the debuff timer itself tick down more slowly or stop (Unceasing Curse and Demon's Gate) can be used to get around this limitation.

Strength
Each debuff has a default strength of its detrimental effect. Like the duration, this can be increased: the strength of a debuff in practice is, where DebuffPower contains any applicable effect that increases debuff strength, such as Swelling Scourge. Some effects, such as the Hellfire Amulet, increase the strength of one particular debuff (in this case, ).

Stacking and replacement
Debuffs do not stack; each character can only have one instance of each debuff at once. Unlike s, a more recently applied instance of a debuff will always override an older instance, even if it has less duration remaining and/or less strength.

Resistance
In most cases, debuffs are not guaranteed; for every hit that can inflict a debuff, there is a certain probability that the debuff will be inflicted. The calculation is as follows: DebuffResistance = BaseDebuffResistance + (sum of FlatDebuffResistance) - (sum of DebuffSuccessPlus) - ResistanceDown

DebuffChance = (BaseDebuffChance - DebuffResistance) * ShackleRingMultiplier where:
 * DebuffChance is the probability that the debuff is inflicted (if it is less than zero or more than one, it is set to 0 or 1 respectively).
 * BaseDebuffResistance is a property of the target; it is 0 on all party members, and varies per enemy as well as the debuff in question (specifically, it depends upon whether the debuff is classified as physical or ether).
 * FlatDebuffResistance contains any bonuses to debuff resistance that the target has, such as Anti-Erosion System. Some sources only provide flat resistance for one debuff, such as Belemnite Bangle. Being significantly under the enemy's results in the enemy having a significant bonus to this value.
 * DebuffSuccessPlus contains any bonuses to debuff success rate that the attacker has. The only source of this available to the party is Sappy-Sappy Drain!.
 * ResistanceDown is the effect of any active Resistance Down debuff on the target.
 * BaseDebuffChance is a fixed value depending upon the debuff (typically between 0.6 and 1).
 * ShackleRingMultiplier is the multiplier from the effect of a Chain Ring, Shackle Ring, or Mighty Link on the Art used to enact the buff (see the linked pages for details), and 1 if this is not applicable.

Reliably inflicting debuffs
Debuffs have one major drawback preventing them from being a combat tool similar in effectiveness to s: reliability. The non-unity debuff chance can easily result in debuff-oriented strategies being inconsistent or even completely ineffective with poor setup. Enemy debuff resistance tends to increase the further one progresses in the game, so while debuffs early-on can be effective by default, it is easy to get to lategame or postgame and experience no success inflicting them at all. While Resistance Down can in theory reduce debuff resistance, it alone is not a consistent means of doing so because it itself can be resisted (and does not have a 100% success rate even when ignoring resistance). Moreover, it is not easy to come by.

There are, however, ways of making debuffs and debuff-oriented strategies consistent. The two main manners in which this is done are Eclipse, 's Ouroboros, and the Shackle Ring (and Chain Ring and Mighty Link, which have the same effect). Eclipse provides a flat additive decrease to the debuff resistance of all enemies, and with a few seconds' setup, Shackle Ring is able to near-double the likelihood of success of a single debuff. The two methods can be used together for additional reliability.

Eclipse is generally the easier of the two options to execute; all it requires is that Taion's Ouroboros form be active (and that Eclipse be unlocked, and ideally levelled up). In particular, it is the best means by which party members can inflict debuffs. Moreover, it naturally comes with the benefit of such debuffs having their duration increased via Unceasing Curse. Its downside is that Taion and cannot take advantage of it (although Taion's Ouroboros can itself provide debuffs, and benefits greatly from them due to Shared Curse). Using this strategy typically requires the option that the player controls the party's Interlinks be selected, to avoid the form being cancelled out of prematurely. Eclipse can be shared with Eunie's Ouroboros to mitigate the effects of the AI swapping off Taion's.

In contrast, Shackle Ring tends to require forethought and some measure of tactics to ensure that the debuffing Art is executed with as big a bonus as possible. The AI cannot be relied upon for this; player control is necessary. For the biggest bonus (assuming a Shackle Ring of any rarity or upgraded Mighty Link), the player should first ensure the list is cleared (most easily done by waiting for a second or two after the previous Art), then use six different Arts, each one cancelled into the next (or used as soon as possible after the previous one finishes). The sixth Art used should be the one which inflicts the desired debuff. Doing so will give the debuff a x1.8 chance of being successful.