Increases the rarity of items dropped by monsters killed using the linked skill.
Since patch 1.0.6, the bonus from this gem applies to enemies killed by degeneration or damage over time effects.[1]
When linked with a skill that creates a minion, trap, mine, or totem, the item rarity modifier does apply to kills made by the minion/trap/mine/totem. This includes deaths caused from Minion Instability explosions.
Since the increased Rarity of Items only applies when landing a killing blow, combining this gem with Culling Strike can be useful when using multiple skills, or while playing in a party, as it increases the chances of the linked skill being the one that lands the killing blow.