Crowd Control (a.k.a. Control Impairing Effects or Status Effects, often abbreviated as CC) is a common term for all negative effects (other than dealing damage or changing the amount of damage received) that can be placed on players or monsters. The name implies their purpose; they are mostly used to buy the attacker time to deal their own damage (or cover their escape), while preventing numerous or overly strong enemies from offensive actions or normal movement.
Crowd Control is mostly used against hordes of lesser enemies to prevent them from overwhelming the player by number, but is also often utilized against single targets to minimize the danger their attacks pose. It can also be used to finish off an enemy while keeping its allies from intervening. In PvP, Crowd Control is especially important, as players are using more cunning tactics, and their combat potential is affected more by all effects that prevent them from acting normally even for a second.
In the original Diablo, only two forms of Crowd Control existed (three if hit animation counts, i.e. microstun, although that is a property of any attack, not a specific trait or skill, and four if one counts the Hellfire-only spells):
Diablo II added more forms, used by both players and monsters, but removed the Stone Curse and Berserk, replacing them with similar, but different mechanics:
- Stun (replaced Stone Curse)
- Slow (including Chill)
- Freeze (replaced Stone Curse)
- Confusion (replaced Berserk)
- Taunt (including Lure)
- Dim Vision
In Diablo III, all of the effects listed above, except Stone Curse/Berserk and Dim Vision, are used, many of them altered compared to Diablo II, one new effect was added, and one was cut prior to release:
Some monsters may be partially or completely immune to some (or even all) forms of Crowd Control, most notably the Bosses being immune to Charm, Knockback and Confusion.
Crowd Control Resistance
Also, in Diablo III monsters have the so-called Crowd Control Resistance for balancing reasons. Each form of Crowd Control has its own resistance, so using one type will not dampen the effectiveness of others.
- Stun, Freeze, Blind, Charm, Fear and all others (except Slow and Knockback) are considered Hard effects, since they render monsters unable to act normally or move. For every second of Hard CC suffered by a monster, it will gain 10% resistance to all Hard CC effects, stacking up to 95%. This will apply to all subsequent Hard effects once the current effect ends.
- Hard Crowd Control effects have a threshold limit: when a monster’s resistance increases to the point that it lowers Hard CC duration below a specific threshold (0.65 seconds for normal monsters, Champions and minions and 0.85 seconds for Rares and Bosses), Hard CC will no longer have any effect on them.
- When a monster is no longer under the effects of Hard CC, its Hard CC resistance will drop by 5% per second until it reaches 0% or encounters another Hard CC effect.
- Slow CC resistance works differently, since they can be constantly re-applied on monsters without duration penalties. Instead, Champions, Minions, Rares, and Bosses reduce the movement-slowing rate of these effects by 25% in relative value (i.e. from 60% movement slow to 45%). For Attack Speed slows, Champions, Minions, Rares, and Bosses reduce the effectiveness of Attack Speed Slows by 65%.
- Knockback and Pull effects will stop functioning when a monster’s Hard CC resistance reaches 65% or greater. Each successful Knockback adds flat 40% Hard CC resistance (20% per tick for effects that continuously apply Knockback, such as Black Hole).
This makes it very hard to control the monster continuously. Monster CC resistance stacks up to a maximum of 95%. In addition, very large monsters are generally immune to Knockback. Both Elites and normal monsters can build resistance to crowd control.
Some monsters are so protected against crowd control effects that very few, if any at all, work on them. Great examples of this could be the Treasure Goblins, and most bosses. For encounters like these, little more than directly damaging the foes will suffice. Other bosses may be affected by certain types of crowd control, or summon regular monsters who are vulnerable to those. Juggernaut Elites are also immune to Crowd Control, at the cost of taking more damage and moving slower.
Players may build up their own CC resistance as well, by stacking the corresponding stat (reduces duration of control impairing effects). This stat can roll up to 40% per item at level 70. It can be stacked all the way up to 100% (though legitimately obtainable maximum is 99.26%), where the effects become nearly unnoticeable. This, however, is multiplicative; as the Nephalem adds to this protection, they will find that its aid weakens. The diminishing returns are calculated as follows: having two items that each increase CC resistance by 40% will grant a total of 64% protection, not 80%, as the total duration of a CC effect would be (1 — 0.4) x (1 — 0.4) = 0.36 = 36%.
Some skills and/or items (for example, Invigorating Gemstone and Bottomless Potion of the Unfettered) may even make players completely immune to some or all forms of CC effects, such as the Cannot Be Frozen affix that allows ignoring Freeze effects. Morphing skills (Barbarian's Wrath of the Berserker, Crusader's Akarat's Champion, Demon Hunter's Vengeance, Wizard's Archon and the Monk's Epiphany) also make the player briefly immune to all forms of CC. In addition, some skills may break one, several or all Crowd Control effects that are already applied to the player character.