What is the dome/bubble around certain enemies in Diablo III?
Sokahr the Keywarden can use several monster traits: Vortex, Mortar, Electrified and Missile Dampening.
Missile Dampening, in particular, has this visual effect:
This trait is shown by a blue dome around the imbued monster. Projectile attacks that enter this sphere have their speed decreased by 90%, making ranged attacks less effective.
