Verified for patch 16.8.1

Horizon Focus

Stunning an enemy causes lightning to strike them, dealing 30% of their max Health as magic damage.

Source

Artifact

Effects

Armor: 20
Health: 250
MagicResist: 20
ManaRegen: 2
PercentHealthDamage: 30

Horizon Focus enables

Stun On the Menu

Disables the target for a duration: no movement, no attacks, no ability casts.