Crowd Control (a.k.a. Control Impairing Effects or Status Effects, often abbreviated as CC) is a common term for all effects (other than dealing damage or changing the amount of damage dealt and 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):
Diablo II added more forms, used by both players and monsters, but removed the Stone Curse:
In Diablo III, all of the effects listed above, except Stone Curse, 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.
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.
- For every second the monster remains under any CC effect, they increase their resistance to that type by 10%
- While free of all CC effects of a certain type, monsters lose 10% CC resistance to that type per second
Accumulated Crowd Control resistance reduces either the effectiveness (such as speed penalty for Slow) or the duration of subsequent (not ongoing) effects of that type by the percentage they have built. This makes it very hard to control the monster continuously with the same effect, but allows doing so with different effects. Monster CC resistance stacks up to a maximum of 95%. While this may not necessarily be enough to ensure complete immunity, some monsters are also immune to Stun effects that are too weak in power, and 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.
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) 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.