Every enemy model killed in close combat by the bearer of the Jagged Dagger must be kept to one side. Each model kept to the side in such a manner may be 'expended' in the Magic phase to allow the bearer to roll an additional power dice.
Source: Warhammer Fantasy: 8th Edition
Every enemy model killed in close combat by the bearer of the Jagged Dagger must be kept to one side. Each model kept to the side in such a manner may be 'expended' in the Magic phase to allow the bearer to roll an additional power dice.