@nirvanstryderWith Mage Slayer, if caster uses Subtle Metamagic to cast spell, would I know and react to attack him? I'd rule that the person with the Mage Slayer feats needs to be aware—by sight or sound—that a spell is being cast.
— Jeremy Crawford (@JeremyECrawford) January 7, 2015
Mage Slayer, if caster uses Subtle Metamagic to cast spell, would I know and react to attack him?
