Immobilise is a secondary status effect in Path of Exile 2.
Overview
Basic Mechanics
What is Immobilise?
Immobilise is a status effect resulting from a target being unable to move. An entity is considered to be Immobilised if they're Heavily Stunned, Pinned, Frozen or Electrocuted, as these effects and Ailments cause a target to be unable to move while they persist.
Note: Immobilise itself does not impart any additional effects on a target.
Immobilise can also be caused by reducing a target's Movement Speed to zero, for example when stacking effects such as Maim and Hinder.
Note: a target is only considered to be Immobilised when their movement is fully prevented.
Chance to Immobilise
Since Immobilise is caused by a primary effect that prevents movement, there's no way to directly apply Immobilise to a target. Instead, you'll need to invest in a way to prevent a target's movement via one or more of the above effects and Ailments.
Duration of Immobilise
The Duration of Immobilise on a target is essentially tied to the Duration of the effect that's preventing a target's movement. While they remain unable to move, they'll be considered as Immobilised.
Utilising Immobilise
Since Immobilise in and of itself does not impart any additional effect, you may be wondering how you can make use of this status effect.
If a target is considered to be Immobilised, you can make use of some modifiers on Skill Gems, Support Gems and items to benefit from this effect. For example
Siege Cascade Quality deals more Damage to Immobilised enemies, whilst the Leverage Support Gem will allow you to more easily deal Critical Hits.
Interactions
Sine Aequo
The Unique Gloves
Sine Aequo will allow you to inflict Immobilising effects at 50% of Buildup instead of 100%, essentially doubling the time it takes you to Immobilise Monsters, but in trade off you'll deal 25% less Damage to Immobilised enemies.