Every time a Wizard successfully casts a spell from the Lore of Tempest, all enemy units within 12" of the Wizard suffer a -1 penalty to their Movement (to a minimum of 1) until the start of the caster's next Magic phase.
Source: Warhammer Armies Project: Unofficial 9th Edition
Every time a Wizard successfully casts a spell from the Lore of Tempest, all enemy units within 12" of the Wizard suffer a -1 penalty to their Movement (to a minimum of 1) until the start of the caster's next Magic phase.