Whenever a spell from the Lore of Yin is successfully cast, all enemy units within 6" of the caster suffer -1 to their armour saves until the start of the caster's next magic phase.
Source: Warhammer Armies Project: Unofficial 9th Edition
Whenever a spell from the Lore of Yin is successfully cast, all enemy units within 6" of the caster suffer -1 to their armour saves until the start of the caster's next magic phase.