RulingRules Reference 1.7

Ultron Ii: If Ultron’s attack is defended by a player other than the one who was attacked, does Ultron get +1 ATK for…

Question

If Ultron’s attack is defended by a player other than the one who was attacked, does Ultron get +1 ATK for each Drone minion engaged with the defending player or the player Ultron initiated the attack against?

Answer

Ultron’s ability has already resolved before defenders are declared, creating a lasting effect that refers to the original target of the attack. The bonus to Ultron’s ATK is based on the number of Drone minions engaged with the player Ultron initiated the attack against. If the number of Drone minions engaged with that player changes, the bonus changes as well.

— Rules Reference 1.7