Cyclone is a level 48 druid ability. It is very similar in mechanics to [Banish]: targets affected by Cyclone cannot move or perform any actions, are immune to receiving heals or buffs, and also completely immune to all incoming damage and unable to be debuffed. Cyclone is affected by diminishing returns, both in PvE and in PvP. Certain versions of this spell cast by monsters CAN be dispelled by [Mass Dispel]. Cyclone has no cooldown.
You can only Cyclone one target at a time. Cycloning a second target will cancel the one currently in effect.
Due to diminishing returns, you will have three successful casts on a single target before immunity begins. This spell's duration is cut in half every time, beginning with 6 seconds, dropping to 3 on the next use, and finally 1.5 seconds.
Any aura or passive buff granted by the affected player or mob to other players or mobs will be temporarily negated until the effect ends. For instance, if you cast Cyclone on a warlock's pet, [Soul Link] will be removed from the warlock and their pet until Cyclone's effect ends.
The target affected by Cyclone is also immune to HoT or DoT effects.
Tips and tactics
Cyclone can be tricky to use because in addition to the affected target being able to perform any actions, no actions may be performed upon the affected target. A Cyclone at the wrong time can cause another player to waste a long cooldown or a high cost spell, whereas a Cyclone at the right time may cause a player to stop casting a long or highly damage attack, or even cause them to not receive a large heal that was coming their way.
Although the Cycloned target is immune to all spells, this does not prevent you from casting spells on them; it will simply have no effect, and the time and mana spent casting will be wasted, as will any cooldowns used. This does however allow you, with a good sense of timing, to begin casting spells on the target in anticipation of the end of the Cyclone.
Using Cyclone as a long-term form of crowd control in an instance can be tricky and difficult for the druid to manage, especially if the druid is the healer. In most situations it is more effective to use [Entangling Roots] if it is necessary to crowd control on a large pull, or continuously throughout an instance. If the target that must be controlled is a ranged attacker however, then Cyclone becomes especially useful.
When using this spell in situations where you're with others, grief can be avoided by communicating how long you will be Cycloning, and when it has gone onto diminishing returns.
Most city raids are always wary of a Cyclone coming down on the tank that has the boss, as the boss will suddenly go after someone squishy.
Patch 9.0.1 (2020-10-13): Now an ability available to all druids