If Damage is replaced or reduced by any means, the replacing or reducing action will include the Bonus Damage in the total damage when determining how much damage is to be dealt. Example: A unit has prevent 3 applied to them. The unit is located at the Void Gate battlefield. An opponent targets the unit with Hextech Ray. Hextech Ray deals 4 damage to the unit, including the Bonus Damage from Void Gate, which the prevent effect will prevent 3 of. The unit takes 1 damage.
§ 715.4.a Core Rules PDF (officieel)
§ 715 Bonus Damage applies to the total damage Dealt by one instance of the action.
§ 715.4 If no damage was Dealt, then Bonus Damage will not apply. Example: Teemo, Strategist is a unit that reads in part “When I defend, choose an enemy unit here and reveal the top 5 cards of your Main Deck. Deal 1 to that unit for each card with Hidden revealed this way, then recycle the revealed cards.”…
