Lacerate Flesh

Lacerate Flesh deals 4 damage to target creature. Create a number of Blood tokens equal to the amount of excess damage dealt to that creature this way. (They're artifacts with "{1}, {T}, Discard a card, Sacrifice this artifact: Draw a card.")

Innistrad: Double Feature

Innistrad: Crimson Vow

A creature has been dealt excess damage if Lacerate Flesh deals more damage to it than the minimum amount of damage required to be lethal damage. In most cases, this means damage greater than the creature's toughness, but take into account any damage that was already dealt to it that turn.